diff --git a/server/database.ts b/server/database.ts
index 2aa6b7b..a88b63e 100644
--- a/server/database.ts
+++ b/server/database.ts
@@ -339,6 +339,10 @@ export const participantOps = {
     db.prepare('DELETE FROM participants WHERE id = ?').run(id);
   },
   
+  update: (id: number, name: string, phone: string | null): void => {
+    db.prepare('UPDATE participants SET name = ?, phone = ? WHERE id = ?').run(name, phone, id);
+  },
+  
   isTokenAvailable: (token: string): boolean => {
     const result = db.prepare('SELECT id FROM participants WHERE token = ?').get(token);
     return !result;
diff --git a/server/routes/admin.ts b/server/routes/admin.ts
index 3baa552..f326d7a 100644
--- a/server/routes/admin.ts
+++ b/server/routes/admin.ts
@@ -225,6 +225,30 @@ router.post('/questionnaires/:id/participants', (req: Request, res: Response) =>
   res.json({ success: true, participant });
 });
 
+// Update participant
+router.put('/participants/:id', (req: Request, res: Response) => {
+  const { name, phone } = req.body;
+  const participant = participantOps.findById(parseInt(req.params.id));
+  
+  if (!participant) {
+    res.status(404).json({ error: 'Deelnemer niet gevonden' });
+    return;
+  }
+  
+  if (!name?.trim()) {
+    res.status(400).json({ error: 'Naam is verplicht' });
+    return;
+  }
+  
+  // Clean phone number (remove spaces, keep + and digits) or set to null if empty
+  const cleanPhone = phone?.trim() ? phone.trim().replace(/[^\d+]/g, '') : null;
+  
+  participantOps.update(participant.id, name.trim(), cleanPhone);
+  const updated = participantOps.findById(participant.id);
+  
+  res.json({ success: true, participant: updated });
+});
+
 // Delete participant
 router.delete('/participants/:id', (req: Request, res: Response) => {
   participantOps.delete(parseInt(req.params.id));
diff --git a/src/pages/QuestionnaireDetail.tsx b/src/pages/QuestionnaireDetail.tsx
index 8f2269f..e1ed010 100644
--- a/src/pages/QuestionnaireDetail.tsx
+++ b/src/pages/QuestionnaireDetail.tsx
@@ -48,6 +48,13 @@ export function QuestionnaireDetail() {
   const [editNameInput, setEditNameInput] = useState('')
   const [editDescriptionInput, setEditDescriptionInput] = useState('')
   const [editLoading, setEditLoading] = useState(false)
+  
+  // Edit participant modal state
+  const [showEditParticipantModal, setShowEditParticipantModal] = useState(false)
+  const [editingParticipant, setEditingParticipant] = useState<Participant | null>(null)
+  const [editParticipantName, setEditParticipantName] = useState('')
+  const [editParticipantPhone, setEditParticipantPhone] = useState('')
+  const [editParticipantLoading, setEditParticipantLoading] = useState(false)
 
   useEffect(() => {
     fetchData()
@@ -153,6 +160,44 @@ export function QuestionnaireDetail() {
     }
   }
 
+  function openEditParticipantModal(participant: Participant) {
+    setEditingParticipant(participant)
+    setEditParticipantName(participant.name)
+    setEditParticipantPhone(participant.phone || '')
+    setShowEditParticipantModal(true)
+  }
+
+  async function handleEditParticipant(e: FormEvent) {
+    e.preventDefault()
+    if (!editingParticipant || !editParticipantName.trim()) return
+
+    setEditParticipantLoading(true)
+    try {
+      const res = await fetch(`/api/admin/participants/${editingParticipant.id}`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        credentials: 'include',
+        body: JSON.stringify({ 
+          name: editParticipantName.trim(),
+          phone: editParticipantPhone.trim() || null
+        }),
+      })
+      const data = await res.json()
+      if (data.success && data.participant) {
+        setShowEditParticipantModal(false)
+        setEditingParticipant(null)
+        // Update the participant in the list
+        setParticipants(participants.map(p => 
+          p.id === editingParticipant.id ? data.participant : p
+        ))
+      }
+    } catch (error) {
+      console.error('Failed to update participant:', error)
+    } finally {
+      setEditParticipantLoading(false)
+    }
+  }
+
   async function handleDelete() {
     if (!confirm('Weet je zeker dat je deze vragenlijst wilt verwijderen? Dit verwijdert ook alle activiteiten en stemmen.')) {
       return
@@ -332,6 +377,13 @@ export function QuestionnaireDetail() {
                         )}
                         <div className="text-xs font-mono text-text-faint truncate mt-1">{participantUrl}</div>
                       </div>
+                      <button
+                        onClick={() => openEditParticipantModal(participant)}
+                        className="px-2 py-1 text-xs font-medium text-text-muted hover:text-accent hover:bg-bg-card rounded transition-colors shrink-0"
+                        title="Bewerken"
+                      >
+                        ✏️
+                      </button>
                       <button
                         onClick={() => handleDeleteParticipant(participant.id)}
                         className="px-2 py-1 text-xs font-medium text-danger hover:bg-danger-muted rounded transition-colors shrink-0"
@@ -516,6 +568,80 @@ export function QuestionnaireDetail() {
           </div>
         </div>
       )}
+
+      {/* Edit Participant Modal */}
+      {showEditParticipantModal && editingParticipant && (
+        <div 
+          className="fixed inset-0 bg-black/70 backdrop-blur-sm flex items-center justify-center z-50 p-4"
+          onClick={() => setShowEditParticipantModal(false)}
+        >
+          <div 
+            className="bg-bg-card border border-border rounded-2xl w-full max-w-md"
+            onClick={(e) => e.stopPropagation()}
+          >
+            {/* Header */}
+            <div className="flex items-center justify-between p-4 border-b border-border">
+              <h3 className="font-semibold text-text">Deelnemer Bewerken</h3>
+              <button 
+                onClick={() => setShowEditParticipantModal(false)}
+                className="text-2xl text-text-muted hover:text-text leading-none"
+              >
+                ×
+              </button>
+            </div>
+
+            {/* Form */}
+            <form onSubmit={handleEditParticipant} className="p-4 space-y-4">
+              <div>
+                <label className="block text-sm font-medium text-text mb-2">
+                  Naam <span className="text-danger">*</span>
+                </label>
+                <input
+                  type="text"
+                  value={editParticipantName}
+                  onChange={(e) => setEditParticipantName(e.target.value)}
+                  className="w-full px-4 py-2 bg-bg-input border border-border rounded-lg text-text placeholder-text-faint focus:outline-none focus:border-accent focus:ring-2 focus:ring-accent/20 transition-colors"
+                  required
+                  autoFocus
+                />
+              </div>
+
+              <div>
+                <label className="block text-sm font-medium text-text mb-2">
+                  Telefoonnummer
+                </label>
+                <input
+                  type="tel"
+                  value={editParticipantPhone}
+                  onChange={(e) => setEditParticipantPhone(e.target.value)}
+                  placeholder="+31612345678 (optioneel, leeg laten om te verwijderen)"
+                  className="w-full px-4 py-2 bg-bg-input border border-border rounded-lg text-text placeholder-text-faint focus:outline-none focus:border-accent focus:ring-2 focus:ring-accent/20 transition-colors"
+                />
+                <p className="text-xs text-text-faint mt-1">
+                  Laat leeg om het telefoonnummer te verwijderen
+                </p>
+              </div>
+
+              <div className="flex gap-3 justify-end pt-2">
+                <button
+                  type="button"
+                  onClick={() => setShowEditParticipantModal(false)}
+                  className="px-4 py-2 border border-border rounded-lg text-text-muted hover:text-text hover:border-text-muted transition-colors"
+                >
+                  Annuleren
+                </button>
+                <button
+                  type="submit"
+                  disabled={editParticipantLoading}
+                  className="px-4 py-2 bg-accent hover:bg-accent-hover text-white font-semibold rounded-lg transition-colors disabled:opacity-50"
+                >
+                  {editParticipantLoading ? 'Opslaan...' : 'Opslaan'}
+                </button>
+              </div>
+            </form>
+          </div>
+        </div>
+      )}
     </div>
   )
 }