diff --git a/backend/app/api/cases.py b/backend/app/api/cases.py
index 14e1208..53bc153 100644
--- a/backend/app/api/cases.py
+++ b/backend/app/api/cases.py
@@ -340,6 +340,49 @@ def set_case_icd(
     return case
 
 
+# ---------------------------------------------------------------------------
+# KVNR update
+# ---------------------------------------------------------------------------
+
+
+@router.put("/{case_id}/kvnr", response_model=CaseResponse)
+def set_case_kvnr(
+    case_id: int,
+    payload: dict,
+    request: Request,
+    db: Session = Depends(get_db),
+    user: User = Depends(get_current_user),
+):
+    """Update the KVNR for a case. Accessible to both admin and dak_mitarbeiter."""
+    case = db.query(Case).filter(Case.id == case_id).first()
+    if not case:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Case not found",
+        )
+
+    old_kvnr = case.kvnr
+    new_kvnr = payload.get("kvnr")
+    case.kvnr = new_kvnr
+    case.updated_by = user.id
+    db.commit()
+    db.refresh(case)
+
+    log_action(
+        db,
+        user_id=user.id,
+        action="kvnr_updated",
+        entity_type="case",
+        entity_id=case.id,
+        old_values={"kvnr": old_kvnr},
+        new_values={"kvnr": new_kvnr},
+        ip_address=request.client.host if request.client else None,
+        user_agent=request.headers.get("user-agent"),
+    )
+
+    return case
+
+
 # ---------------------------------------------------------------------------
 # Coding (Gutachten classification)
 # ---------------------------------------------------------------------------
diff --git a/frontend/src/pages/CasesPage.tsx b/frontend/src/pages/CasesPage.tsx
index 1a541a4..cc66288 100644
--- a/frontend/src/pages/CasesPage.tsx
+++ b/frontend/src/pages/CasesPage.tsx
@@ -311,16 +311,36 @@ function CaseDetail({
   onIcdSaved: (updated: Case) => void
 }) {
   const [icdValue, setIcdValue] = useState(caseData.icd || '')
+  const [kvnrValue, setKvnrValue] = useState(caseData.kvnr || '')
   const [saving, setSaving] = useState(false)
+  const [savingKvnr, setSavingKvnr] = useState(false)
   const [error, setError] = useState('')
   const [success, setSuccess] = useState(false)
+  const [kvnrSuccess, setKvnrSuccess] = useState(false)
 
   // Reset on case change
   useEffect(() => {
     setIcdValue(caseData.icd || '')
+    setKvnrValue(caseData.kvnr || '')
     setError('')
     setSuccess(false)
-  }, [caseData.id, caseData.icd])
+    setKvnrSuccess(false)
+  }, [caseData.id, caseData.icd, caseData.kvnr])
+
+  const saveKvnr = async () => {
+    setSavingKvnr(true)
+    setError('')
+    setKvnrSuccess(false)
+    try {
+      const res = await api.put<Case>(`/cases/${caseData.id}/kvnr`, { kvnr: kvnrValue.trim() || null })
+      onIcdSaved(res.data)
+      setKvnrSuccess(true)
+    } catch {
+      setError('Fehler beim Speichern der KVNR.')
+    } finally {
+      setSavingKvnr(false)
+    }
+  }
 
   const saveIcd = async () => {
     if (!icdValue.trim()) return
@@ -361,7 +381,29 @@ function CaseDetail({
           <DetailField label="Vorname" value={caseData.vorname} />
           <DetailField label="Nachname" value={caseData.nachname} />
           <DetailField label="Geburtsdatum" value={caseData.geburtsdatum ? formatDate(caseData.geburtsdatum) : null} />
-          <DetailField label="KVNR" value={caseData.kvnr} />
+          <div className="col-span-2">
+            <label className="text-sm text-muted-foreground">KVNR (Versichertennummer)</label>
+            <div className="flex gap-2 mt-1">
+              <Input
+                value={kvnrValue}
+                onChange={(e) => { setKvnrValue(e.target.value); setKvnrSuccess(false) }}
+                placeholder="z.B. A123456789"
+                className="flex-1 font-mono"
+              />
+              <Button
+                size="sm"
+                variant="outline"
+                onClick={saveKvnr}
+                disabled={savingKvnr || kvnrValue === (caseData.kvnr || '')}
+              >
+                <Save className="size-4 mr-1" />
+                {savingKvnr ? '...' : 'Speichern'}
+              </Button>
+            </div>
+            {kvnrSuccess && (
+              <p className="text-sm text-green-600 mt-1">KVNR gespeichert.</p>
+            )}
+          </div>
           <DetailField label="Versicherung" value={caseData.versicherung} />
         </div>