diff --git a/src/app/api/v1/berths/[id]/activity/route.ts b/src/app/api/v1/berths/[id]/activity/route.ts
new file mode 100644
index 0000000..09beead
--- /dev/null
+++ b/src/app/api/v1/berths/[id]/activity/route.ts
@@ -0,0 +1,31 @@
+import { NextResponse } from 'next/server';
+import { eq, and } from 'drizzle-orm';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { db } from '@/lib/db';
+import { berths } from '@/lib/db/schema/berths';
+import { loadEntityActivity } from '@/lib/services/entity-activity.service';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+
+export const GET = withAuth(
+  withPermission('berths', 'view', async (_req, ctx, params) => {
+    try {
+      const id = params.id;
+      if (!id) throw new NotFoundError('berth');
+      const exists = await db
+        .select({ id: berths.id })
+        .from(berths)
+        .where(and(eq(berths.id, id), eq(berths.portId, ctx.portId)))
+        .limit(1);
+      if (exists.length === 0) throw new NotFoundError('berth');
+      const data = await loadEntityActivity({
+        portId: ctx.portId,
+        entityType: 'berth',
+        entityId: id,
+      });
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/app/api/v1/clients/[id]/activity/route.ts b/src/app/api/v1/clients/[id]/activity/route.ts
new file mode 100644
index 0000000..fe38276
--- /dev/null
+++ b/src/app/api/v1/clients/[id]/activity/route.ts
@@ -0,0 +1,31 @@
+import { NextResponse } from 'next/server';
+import { eq, and } from 'drizzle-orm';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { db } from '@/lib/db';
+import { clients } from '@/lib/db/schema/clients';
+import { loadEntityActivity } from '@/lib/services/entity-activity.service';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+
+export const GET = withAuth(
+  withPermission('clients', 'view', async (_req, ctx, params) => {
+    try {
+      const id = params.id;
+      if (!id) throw new NotFoundError('client');
+      const exists = await db
+        .select({ id: clients.id })
+        .from(clients)
+        .where(and(eq(clients.id, id), eq(clients.portId, ctx.portId)))
+        .limit(1);
+      if (exists.length === 0) throw new NotFoundError('client');
+      const data = await loadEntityActivity({
+        portId: ctx.portId,
+        entityType: 'client',
+        entityId: id,
+      });
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/app/api/v1/companies/[id]/activity/route.ts b/src/app/api/v1/companies/[id]/activity/route.ts
new file mode 100644
index 0000000..182de99
--- /dev/null
+++ b/src/app/api/v1/companies/[id]/activity/route.ts
@@ -0,0 +1,31 @@
+import { NextResponse } from 'next/server';
+import { eq, and } from 'drizzle-orm';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { db } from '@/lib/db';
+import { companies } from '@/lib/db/schema/companies';
+import { loadEntityActivity } from '@/lib/services/entity-activity.service';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+
+export const GET = withAuth(
+  withPermission('companies', 'view', async (_req, ctx, params) => {
+    try {
+      const id = params.id;
+      if (!id) throw new NotFoundError('company');
+      const exists = await db
+        .select({ id: companies.id })
+        .from(companies)
+        .where(and(eq(companies.id, id), eq(companies.portId, ctx.portId)))
+        .limit(1);
+      if (exists.length === 0) throw new NotFoundError('company');
+      const data = await loadEntityActivity({
+        portId: ctx.portId,
+        entityType: 'company',
+        entityId: id,
+      });
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/app/api/v1/interests/[id]/activity/route.ts b/src/app/api/v1/interests/[id]/activity/route.ts
new file mode 100644
index 0000000..8180d88
--- /dev/null
+++ b/src/app/api/v1/interests/[id]/activity/route.ts
@@ -0,0 +1,31 @@
+import { NextResponse } from 'next/server';
+import { eq, and } from 'drizzle-orm';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { db } from '@/lib/db';
+import { interests } from '@/lib/db/schema/interests';
+import { loadEntityActivity } from '@/lib/services/entity-activity.service';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+
+export const GET = withAuth(
+  withPermission('interests', 'view', async (_req, ctx, params) => {
+    try {
+      const id = params.id;
+      if (!id) throw new NotFoundError('interest');
+      const exists = await db
+        .select({ id: interests.id })
+        .from(interests)
+        .where(and(eq(interests.id, id), eq(interests.portId, ctx.portId)))
+        .limit(1);
+      if (exists.length === 0) throw new NotFoundError('interest');
+      const data = await loadEntityActivity({
+        portId: ctx.portId,
+        entityType: 'interest',
+        entityId: id,
+      });
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/app/api/v1/yachts/[id]/activity/route.ts b/src/app/api/v1/yachts/[id]/activity/route.ts
new file mode 100644
index 0000000..1253bc1
--- /dev/null
+++ b/src/app/api/v1/yachts/[id]/activity/route.ts
@@ -0,0 +1,31 @@
+import { NextResponse } from 'next/server';
+import { eq, and } from 'drizzle-orm';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { db } from '@/lib/db';
+import { yachts } from '@/lib/db/schema/yachts';
+import { loadEntityActivity } from '@/lib/services/entity-activity.service';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+
+export const GET = withAuth(
+  withPermission('yachts', 'view', async (_req, ctx, params) => {
+    try {
+      const id = params.id;
+      if (!id) throw new NotFoundError('yacht');
+      const exists = await db
+        .select({ id: yachts.id })
+        .from(yachts)
+        .where(and(eq(yachts.id, id), eq(yachts.portId, ctx.portId)))
+        .limit(1);
+      if (exists.length === 0) throw new NotFoundError('yacht');
+      const data = await loadEntityActivity({
+        portId: ctx.portId,
+        entityType: 'yacht',
+        entityId: id,
+      });
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);
diff --git a/src/components/berths/berth-tabs.tsx b/src/components/berths/berth-tabs.tsx
index 89e6e26..f057419 100644
--- a/src/components/berths/berth-tabs.tsx
+++ b/src/components/berths/berth-tabs.tsx
@@ -3,6 +3,7 @@
 import { type DetailTab } from '@/components/shared/detail-layout';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import { TagBadge } from '@/components/shared/tag-badge';
+import { EntityActivityFeed } from '@/components/shared/entity-activity-feed';
 import { BerthReservationsTab } from './berth-reservations-tab';
 import { BerthInterestsTab } from './berth-interests-tab';
 import { BerthInterestPulse } from './berth-interest-pulse';
@@ -250,7 +251,12 @@ export function buildBerthTabs(berth: BerthData): DetailTab[] {
     {
       id: 'activity',
       label: 'Activity',
-      content: <StubTab label="Activity" />,
+      content: (
+        <EntityActivityFeed
+          endpoint={`/api/v1/berths/${berth.id}/activity`}
+          emptyText="No activity recorded for this berth yet."
+        />
+      ),
     },
   ];
 }
diff --git a/src/components/clients/client-tabs.tsx b/src/components/clients/client-tabs.tsx
index b4ca8e4..05b4243 100644
--- a/src/components/clients/client-tabs.tsx
+++ b/src/components/clients/client-tabs.tsx
@@ -16,6 +16,7 @@ import { ClientCompaniesTab } from '@/components/clients/client-companies-tab';
 import { ClientReservationsTab } from '@/components/clients/client-reservations-tab';
 import { ContactsEditor } from '@/components/clients/contacts-editor';
 import { AddressesEditor, type Address } from '@/components/shared/addresses-editor';
+import { EntityActivityFeed } from '@/components/shared/entity-activity-feed';
 import { apiFetch } from '@/lib/api/client';
 
 type ClientPatchField =
@@ -280,9 +281,10 @@ export function getClientTabs({ clientId, currentUserId, client }: ClientTabsOpt
       id: 'activity',
       label: 'Activity',
       content: (
-        <div className="text-center py-12 text-muted-foreground">
-          <p>Activity log coming soon.</p>
-        </div>
+        <EntityActivityFeed
+          endpoint={`/api/v1/clients/${clientId}/activity`}
+          emptyText="No activity recorded for this client yet."
+        />
       ),
     },
   ];
diff --git a/src/components/companies/company-tabs.tsx b/src/components/companies/company-tabs.tsx
index a779552..59b147b 100644
--- a/src/components/companies/company-tabs.tsx
+++ b/src/components/companies/company-tabs.tsx
@@ -9,6 +9,7 @@ import { InlineCountryField } from '@/components/shared/inline-country-field';
 import { SubdivisionCombobox } from '@/components/shared/subdivision-combobox';
 import { InlineTagEditor } from '@/components/shared/inline-tag-editor';
 import { NotesList } from '@/components/shared/notes-list';
+import { EntityActivityFeed } from '@/components/shared/entity-activity-feed';
 import { CompanyMembersTab } from '@/components/companies/company-members-tab';
 import { CompanyOwnedYachtsTab } from '@/components/companies/company-owned-yachts-tab';
 import { AddressesEditor, type Address } from '@/components/shared/addresses-editor';
@@ -238,5 +239,15 @@ export function getCompanyTabs({
         <NotesList entityType="companies" entityId={companyId} currentUserId={currentUserId} />
       ),
     },
+    {
+      id: 'activity',
+      label: 'Activity',
+      content: (
+        <EntityActivityFeed
+          endpoint={`/api/v1/companies/${companyId}/activity`}
+          emptyText="No activity recorded for this company yet."
+        />
+      ),
+    },
   ];
 }
diff --git a/src/components/shared/entity-activity-feed.tsx b/src/components/shared/entity-activity-feed.tsx
new file mode 100644
index 0000000..661c0c0
--- /dev/null
+++ b/src/components/shared/entity-activity-feed.tsx
@@ -0,0 +1,122 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { formatDistanceToNow } from 'date-fns';
+
+import { apiFetch } from '@/lib/api/client';
+
+interface AuditRow {
+  id: string;
+  action: string;
+  entityType: string;
+  entityId: string | null;
+  fieldChanged: string | null;
+  oldValue: unknown;
+  newValue: unknown;
+  metadata: Record<string, unknown> | null;
+  createdAt: string;
+  actor: { id: string; email: string; name: string | null } | null;
+}
+
+const ACTION_LABELS: Record<string, string> = {
+  create: 'Created',
+  update: 'Updated',
+  delete: 'Deleted',
+  archive: 'Archived',
+  restore: 'Restored',
+  merge: 'Merged',
+  revert: 'Reverted',
+};
+
+function formatAction(action: string): string {
+  return ACTION_LABELS[action] ?? action.charAt(0).toUpperCase() + action.slice(1);
+}
+
+function formatField(field: string | null): string | null {
+  if (!field) return null;
+  return field.replace(/_/g, ' ');
+}
+
+function summarize(row: AuditRow): string {
+  const verb = formatAction(row.action);
+  const field = formatField(row.fieldChanged);
+  if (field) return `${verb} ${field}`;
+  return verb;
+}
+
+interface Props {
+  endpoint: string; // e.g. /api/v1/clients/{id}/activity
+  emptyText?: string;
+}
+
+export function EntityActivityFeed({ endpoint, emptyText = 'No activity yet.' }: Props) {
+  const [now, setNow] = useState(() => Date.now());
+
+  // Re-render every minute so "x minutes ago" stays accurate without a
+  // refetch.
+  useEffect(() => {
+    const t = setInterval(() => setNow(Date.now()), 60_000);
+    return () => clearInterval(t);
+  }, []);
+
+  const { data, isLoading, error } = useQuery({
+    queryKey: ['entity-activity', endpoint],
+    queryFn: () => apiFetch<{ data: AuditRow[] }>(endpoint),
+    staleTime: 30_000,
+  });
+
+  if (isLoading) {
+    return <div className="text-sm text-muted-foreground py-6">Loading activity…</div>;
+  }
+  if (error) {
+    return (
+      <div className="text-sm text-red-600 py-6">
+        Failed to load activity: {error instanceof Error ? error.message : 'unknown error'}
+      </div>
+    );
+  }
+
+  const rows = data?.data ?? [];
+  if (rows.length === 0) {
+    return <div className="text-sm text-muted-foreground py-6">{emptyText}</div>;
+  }
+
+  return (
+    <ol className="relative border-l border-muted-foreground/20 ml-3 pl-6 space-y-4 py-2">
+      {rows.map((row) => {
+        const created = new Date(row.createdAt);
+        const ago = formatDistanceToNow(created, { addSuffix: true });
+        // touch `now` so the closure participates in the minute re-render
+        void now;
+        const actor = row.actor?.name || row.actor?.email || 'System';
+        return (
+          <li key={row.id} className="relative">
+            <span className="absolute -left-[31px] top-1 h-2.5 w-2.5 rounded-full bg-primary/70 ring-2 ring-background" />
+            <div className="text-sm">
+              <span className="font-medium">{summarize(row)}</span>
+              <span className="text-muted-foreground"> · {actor}</span>
+            </div>
+            <div className="text-xs text-muted-foreground" title={created.toISOString()}>
+              {ago}
+            </div>
+            {row.fieldChanged && (row.oldValue !== null || row.newValue !== null) ? (
+              <div className="mt-1 text-xs space-x-2">
+                {row.oldValue !== null && row.oldValue !== undefined ? (
+                  <span className="line-through text-muted-foreground">
+                    {String(JSON.stringify(row.oldValue)).slice(0, 80)}
+                  </span>
+                ) : null}
+                {row.newValue !== null && row.newValue !== undefined ? (
+                  <span className="text-foreground">
+                    → {String(JSON.stringify(row.newValue)).slice(0, 80)}
+                  </span>
+                ) : null}
+              </div>
+            ) : null}
+          </li>
+        );
+      })}
+    </ol>
+  );
+}
diff --git a/src/components/yachts/yacht-tabs.tsx b/src/components/yachts/yacht-tabs.tsx
index 7459513..e97e6b2 100644
--- a/src/components/yachts/yacht-tabs.tsx
+++ b/src/components/yachts/yacht-tabs.tsx
@@ -7,6 +7,7 @@ import type { DetailTab } from '@/components/shared/detail-layout';
 import { InlineEditableField } from '@/components/shared/inline-editable-field';
 import { InlineTagEditor } from '@/components/shared/inline-tag-editor';
 import { NotesList } from '@/components/shared/notes-list';
+import { EntityActivityFeed } from '@/components/shared/entity-activity-feed';
 import { ReservationList, type ReservationRow } from '@/components/reservations/reservation-list';
 import { YachtOwnershipHistory } from '@/components/yachts/yacht-ownership-history';
 import { apiFetch } from '@/lib/api/client';
@@ -225,7 +226,15 @@ function YachtInterestsTab({ yachtId }: { yachtId: string }) {
 
   if (isLoading) return <p className="text-sm text-muted-foreground">Loading…</p>;
   if (interests.length === 0) {
-    return <p className="text-sm text-muted-foreground">No interests linked to this yacht.</p>;
+    return (
+      <div className="rounded-md border border-dashed bg-muted/30 p-6 text-center">
+        <p className="text-sm font-medium">No interests linked to this yacht</p>
+        <p className="text-xs text-muted-foreground mt-1">
+          Interests for this yacht will appear here once a sales rep links them. Add an interest
+          from the Interests tab on the owner&rsquo;s client page.
+        </p>
+      </div>
+    );
   }
 
   return (
@@ -298,5 +307,15 @@ export function getYachtTabs({ yachtId, currentUserId, yacht }: YachtTabsOptions
       label: 'Notes',
       content: <NotesList entityType="yachts" entityId={yachtId} currentUserId={currentUserId} />,
     },
+    {
+      id: 'activity',
+      label: 'Activity',
+      content: (
+        <EntityActivityFeed
+          endpoint={`/api/v1/yachts/${yachtId}/activity`}
+          emptyText="No activity recorded for this yacht yet."
+        />
+      ),
+    },
   ];
 }
diff --git a/src/lib/services/entity-activity.service.ts b/src/lib/services/entity-activity.service.ts
new file mode 100644
index 0000000..15b2471
--- /dev/null
+++ b/src/lib/services/entity-activity.service.ts
@@ -0,0 +1,42 @@
+import { inArray } from 'drizzle-orm';
+
+import { db } from '@/lib/db';
+import { user } from '@/lib/db/schema/users';
+import { searchAuditLogs } from '@/lib/services/audit-search.service';
+
+/**
+ * Shared loader for the per-entity Activity tab. Wraps `searchAuditLogs`
+ * with actor-email resolution so each row can render `who did what`.
+ *
+ * Tenant gate happens at the API route — this service trusts the caller
+ * to pass an entityId that belongs to `portId`.
+ */
+export async function loadEntityActivity(args: {
+  portId: string;
+  entityType: string;
+  entityId: string;
+  limit?: number;
+}) {
+  const { rows } = await searchAuditLogs({
+    portId: args.portId,
+    entityType: args.entityType,
+    entityId: args.entityId,
+    limit: args.limit ?? 50,
+  });
+
+  const userIds = Array.from(
+    new Set(rows.map((r) => r.userId).filter((u): u is string => Boolean(u))),
+  );
+  const userRows = userIds.length
+    ? await db
+        .select({ id: user.id, email: user.email, name: user.name })
+        .from(user)
+        .where(inArray(user.id, userIds))
+    : [];
+  const userMap = new Map(userRows.map((u) => [u.id, u]));
+
+  return rows.map((r) => ({
+    ...r,
+    actor: r.userId ? (userMap.get(r.userId) ?? null) : null,
+  }));
+}