diff --git a/src/components/yachts/yacht-detail-header.tsx b/src/components/yachts/yacht-detail-header.tsx
index 5204538..99b8a14 100644
--- a/src/components/yachts/yacht-detail-header.tsx
+++ b/src/components/yachts/yacht-detail-header.tsx
@@ -9,16 +9,10 @@ import { toast } from 'sonner';
 
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
-import {
-  Dialog,
-  DialogContent,
-  DialogDescription,
-  DialogFooter,
-  DialogHeader,
-  DialogTitle,
-} from '@/components/ui/dialog';
 import { ArchiveConfirmDialog } from '@/components/shared/archive-confirm-dialog';
+import { PermissionGate } from '@/components/shared/permission-gate';
 import { YachtForm } from '@/components/yachts/yacht-form';
+import { YachtTransferDialog } from '@/components/yachts/yacht-transfer-dialog';
 import { apiFetch } from '@/lib/api/client';
 
 interface YachtDetailHeaderYacht {
@@ -174,15 +168,17 @@ export function YachtDetailHeader({ yacht }: YachtDetailHeaderProps) {
               <Pencil className="mr-1.5 h-3.5 w-3.5" />
               Edit
             </Button>
-            <Button
-              variant="outline"
-              size="sm"
-              onClick={() => setTransferOpen(true)}
-              disabled={isArchived}
-            >
-              <ArrowRightLeft className="mr-1.5 h-3.5 w-3.5" />
-              Transfer
-            </Button>
+            <PermissionGate resource="yachts" action="transfer">
+              <Button
+                variant="outline"
+                size="sm"
+                onClick={() => setTransferOpen(true)}
+                disabled={isArchived}
+              >
+                <ArrowRightLeft className="mr-1.5 h-3.5 w-3.5" />
+                Transfer
+              </Button>
+            </PermissionGate>
             <Button
               variant="outline"
               size="sm"
@@ -234,30 +230,12 @@ export function YachtDetailHeader({ yacht }: YachtDetailHeaderProps) {
         isLoading={archiveMutation.isPending}
       />
 
-      {/* TODO(Task 5.5): Replace with real YachtTransferDialog component. */}
-      <Dialog open={transferOpen} onOpenChange={setTransferOpen}>
-        <DialogContent>
-          <DialogHeader>
-            <DialogTitle>Transfer Ownership</DialogTitle>
-            <DialogDescription>
-              The yacht ownership transfer flow will be implemented in Task 5.5.
-            </DialogDescription>
-          </DialogHeader>
-          <div className="py-2 text-sm text-muted-foreground">
-            This stub will be replaced with a form that lets you pick a new owner, effective date,
-            reason, and notes — then calls{' '}
-            <code className="rounded bg-muted px-1 text-xs">
-              POST /api/v1/yachts/{'{id}'}/transfer
-            </code>
-            .
-          </div>
-          <DialogFooter>
-            <Button variant="outline" onClick={() => setTransferOpen(false)}>
-              Close
-            </Button>
-          </DialogFooter>
-        </DialogContent>
-      </Dialog>
+      <YachtTransferDialog
+        open={transferOpen}
+        onOpenChange={setTransferOpen}
+        yachtId={yacht.id}
+        currentOwner={{ type: yacht.currentOwnerType, id: yacht.currentOwnerId }}
+      />
     </>
   );
 }
diff --git a/src/components/yachts/yacht-transfer-dialog.tsx b/src/components/yachts/yacht-transfer-dialog.tsx
new file mode 100644
index 0000000..e89ec26
--- /dev/null
+++ b/src/components/yachts/yacht-transfer-dialog.tsx
@@ -0,0 +1,202 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { useForm } from 'react-hook-form';
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { Loader2 } from 'lucide-react';
+import { toast } from 'sonner';
+
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import { Button } from '@/components/ui/button';
+import { Label } from '@/components/ui/label';
+import { Input } from '@/components/ui/input';
+import { Textarea } from '@/components/ui/textarea';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { OwnerPicker, type OwnerRef } from '@/components/shared/owner-picker';
+import { apiFetch } from '@/lib/api/client';
+
+type TransferReason = 'sale' | 'inheritance' | 'gift' | 'company_restructure' | 'other';
+
+type FormValues = {
+  newOwner: OwnerRef | undefined;
+  effectiveDate: string; // ISO date string from <input type="date">
+  transferReason?: TransferReason;
+  transferNotes?: string;
+};
+
+interface YachtTransferDialogProps {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  yachtId: string;
+  /** Current owner shown for reference; used to guard against selecting the same owner. */
+  currentOwner?: OwnerRef;
+}
+
+const todayIso = (): string => new Date().toISOString().slice(0, 10);
+
+export function YachtTransferDialog({
+  open,
+  onOpenChange,
+  yachtId,
+  currentOwner,
+}: YachtTransferDialogProps) {
+  const queryClient = useQueryClient();
+  const [formError, setFormError] = useState<string | null>(null);
+
+  const {
+    register,
+    handleSubmit,
+    watch,
+    setValue,
+    reset,
+    formState: { errors, isSubmitting },
+  } = useForm<FormValues>({
+    defaultValues: {
+      newOwner: undefined,
+      effectiveDate: todayIso(),
+      transferReason: undefined,
+      transferNotes: '',
+    },
+  });
+
+  useEffect(() => {
+    if (open) {
+      setFormError(null);
+      reset({
+        newOwner: undefined,
+        effectiveDate: todayIso(),
+        transferReason: undefined,
+        transferNotes: '',
+      });
+    }
+  }, [open, reset]);
+
+  const newOwner = watch('newOwner');
+  const transferReason = watch('transferReason');
+
+  const mutation = useMutation({
+    mutationFn: async (data: FormValues) => {
+      if (!data.newOwner) {
+        throw new Error('Please select a new owner');
+      }
+      if (
+        currentOwner &&
+        data.newOwner.type === currentOwner.type &&
+        data.newOwner.id === currentOwner.id
+      ) {
+        throw new Error('New owner must be different from the current owner');
+      }
+      await apiFetch(`/api/v1/yachts/${yachtId}/transfer`, {
+        method: 'POST',
+        body: {
+          newOwner: data.newOwner,
+          effectiveDate: data.effectiveDate,
+          transferReason: data.transferReason,
+          transferNotes: data.transferNotes?.trim() || undefined,
+        },
+      });
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['yachts', yachtId] });
+      queryClient.invalidateQueries({ queryKey: ['yachts', yachtId, 'ownership-history'] });
+      queryClient.invalidateQueries({ queryKey: ['yachts'] });
+      toast.success('Ownership transferred');
+      onOpenChange(false);
+    },
+    onError: (err: unknown) => {
+      const msg = err instanceof Error ? err.message : 'Failed to transfer ownership';
+      setFormError(msg);
+    },
+  });
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="max-w-md">
+        <DialogHeader>
+          <DialogTitle>Transfer ownership</DialogTitle>
+          <DialogDescription>
+            This will close the current ownership record and open a new one. The change is auditable
+            and atomic.
+          </DialogDescription>
+        </DialogHeader>
+
+        <form
+          onSubmit={handleSubmit((data) => {
+            setFormError(null);
+            mutation.mutate(data);
+          })}
+          className="space-y-4"
+        >
+          <div className="space-y-2">
+            <Label>New owner</Label>
+            <OwnerPicker
+              value={newOwner ?? null}
+              onChange={(v) => setValue('newOwner', v ?? undefined)}
+            />
+          </div>
+
+          <div className="space-y-2">
+            <Label htmlFor="effectiveDate">Effective date</Label>
+            <Input
+              id="effectiveDate"
+              type="date"
+              {...register('effectiveDate', { required: true })}
+            />
+            {errors.effectiveDate && <p className="text-xs text-destructive">Required</p>}
+          </div>
+
+          <div className="space-y-2">
+            <Label>Reason (optional)</Label>
+            <Select
+              onValueChange={(v) => setValue('transferReason', v as TransferReason)}
+              value={transferReason ?? ''}
+            >
+              <SelectTrigger>
+                <SelectValue placeholder="Select a reason..." />
+              </SelectTrigger>
+              <SelectContent>
+                <SelectItem value="sale">Sale</SelectItem>
+                <SelectItem value="inheritance">Inheritance</SelectItem>
+                <SelectItem value="gift">Gift</SelectItem>
+                <SelectItem value="company_restructure">Company restructure</SelectItem>
+                <SelectItem value="other">Other</SelectItem>
+              </SelectContent>
+            </Select>
+          </div>
+
+          <div className="space-y-2">
+            <Label htmlFor="transferNotes">Notes (optional)</Label>
+            <Textarea id="transferNotes" rows={3} {...register('transferNotes')} />
+          </div>
+
+          {formError && <p className="text-sm text-destructive">{formError}</p>}
+
+          <DialogFooter>
+            <Button type="button" variant="outline" onClick={() => onOpenChange(false)}>
+              Cancel
+            </Button>
+            <Button type="submit" disabled={isSubmitting || mutation.isPending}>
+              {(isSubmitting || mutation.isPending) && (
+                <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+              )}
+              Transfer
+            </Button>
+          </DialogFooter>
+        </form>
+      </DialogContent>
+    </Dialog>
+  );
+}