diff --git a/web/src/components/CreateTimerModal.tsx b/web/src/components/CreateTimerModal.tsx
index 6833bea..c8265e0 100644
--- a/web/src/components/CreateTimerModal.tsx
+++ b/web/src/components/CreateTimerModal.tsx
@@ -10,6 +10,7 @@ import { X, AlarmClock, Timer, Coffee, Sparkles, CalendarDays } from 'lucide-rea
 import { BUILT_IN_CATEGORIES, getCategoryById } from '@/lib/categories';
 import { parseNaturalLanguage } from '@/lib/nl-parser';
 import type { ParseResult } from '@/lib/nl-parser';
+import { alarmSchema, countdownSchema, pomodoroSchema, eventSchema } from '@/lib/schemas';
 
 type TabType = 'alarm' | 'countdown' | 'pomodoro' | 'event';
 
@@ -46,6 +47,9 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
   // Event fields
   const [eventDate, setEventDate] = useState('');
 
+  // Validation errors
+  const [errors, setErrors] = useState<Record<string, string>>({});
+
   if (!isOpen) return null;
 
   const handleNlChange = (value: string) => {
@@ -100,11 +104,18 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
   };
 
   const handleCreate = () => {
+    setErrors({});
     const cascade = { preset: cascadePreset, intervals: [] as number[] };
     const catOrUndef = category || undefined;
 
     if (tab === 'alarm') {
-      if (!alarmTime) return;
+      const result = alarmSchema.safeParse({ label: label || 'Alarm', alarmTime, urgency, cascadePreset });
+      if (!result.success) {
+        const fieldErrors: Record<string, string> = {};
+        for (const issue of result.error.issues) { fieldErrors[issue.path[0] as string] = issue.message; }
+        setErrors(fieldErrors);
+        return;
+      }
       const [h, m] = alarmTime.split(':').map(Number);
       const target = new Date();
       target.setHours(h, m, 0, 0);
@@ -112,25 +123,38 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
         target.setDate(target.getDate() + 1);
       }
       addAlarm({
-        label: label || 'Alarm',
+        label: result.data.label,
         targetTime: target.getTime(),
         urgency,
         cascade,
         category: catOrUndef,
       });
     } else if (tab === 'countdown') {
+      const result = countdownSchema.safeParse({ label: label || 'Countdown', hours, minutes, seconds, urgency, cascadePreset });
+      if (!result.success) {
+        const fieldErrors: Record<string, string> = {};
+        for (const issue of result.error.issues) { fieldErrors[issue.path[0] as string] = issue.message; }
+        setErrors(fieldErrors);
+        return;
+      }
       const durationMs = (hours * 3600 + minutes * 60 + seconds) * 1000;
-      if (durationMs <= 0) return;
       addCountdown({
-        label: label || 'Countdown',
+        label: result.data.label,
         durationMs,
         urgency,
         cascade,
         category: catOrUndef,
       });
     } else if (tab === 'pomodoro') {
+      const result = pomodoroSchema.safeParse({ label: label || 'Focus Session', workMinutes: workMin, breakMinutes: breakMin, longBreakMinutes: longBreakMin, rounds, urgency });
+      if (!result.success) {
+        const fieldErrors: Record<string, string> = {};
+        for (const issue of result.error.issues) { fieldErrors[issue.path[0] as string] = issue.message; }
+        setErrors(fieldErrors);
+        return;
+      }
       addPomodoro({
-        label: label || 'Focus Session',
+        label: result.data.label,
         config: {
           workMinutes: workMin,
           breakMinutes: breakMin,
@@ -140,11 +164,16 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
         urgency,
       });
     } else if (tab === 'event') {
-      if (!eventDate) return;
+      const result = eventSchema.safeParse({ label: label || 'Event Countdown', eventDate, urgency, cascadePreset });
+      if (!result.success) {
+        const fieldErrors: Record<string, string> = {};
+        for (const issue of result.error.issues) { fieldErrors[issue.path[0] as string] = issue.message; }
+        setErrors(fieldErrors);
+        return;
+      }
       const target = new Date(eventDate).getTime();
-      if (target <= Date.now()) return;
       addEvent({
-        label: label || 'Event Countdown',
+        label: result.data.label,
         targetTime: target,
         urgency,
         category: catOrUndef,
@@ -159,6 +188,7 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
     setSeconds(0);
     setCategory('');
     setEventDate('');
+    setErrors({});
     onClose();
   };
 
@@ -276,10 +306,11 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
               className="w-full px-3 py-2 rounded-lg border text-sm focus:outline-none focus:ring-2"
               style={{
                 backgroundColor: 'var(--cm-surface-card)',
-                borderColor: 'var(--cm-border)',
+                borderColor: errors.label ? 'var(--cm-danger)' : 'var(--cm-border)',
                 color: 'var(--cm-text-primary)',
               }}
             />
+            {errors.label && <p className="text-xs mt-1" style={{ color: 'var(--cm-danger)' }}>{errors.label}</p>}
           </div>
 
           {/* Tab-specific fields */}
@@ -295,10 +326,11 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
                 className="w-full px-3 py-2 rounded-lg border text-sm focus:outline-none focus:ring-2"
                 style={{
                   backgroundColor: 'var(--cm-surface-card)',
-                  borderColor: 'var(--cm-border)',
+                  borderColor: errors.alarmTime ? 'var(--cm-danger)' : 'var(--cm-border)',
                   color: 'var(--cm-text-primary)',
                 }}
               />
+              {errors.alarmTime && <p className="text-xs mt-1" style={{ color: 'var(--cm-danger)' }}>{errors.alarmTime}</p>}
             </div>
           )}
 
@@ -333,6 +365,7 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
                   </div>
                 ))}
               </div>
+              {errors.minutes && <p className="text-xs mt-1" style={{ color: 'var(--cm-danger)' }}>{errors.minutes}</p>}
               {/* Quick presets */}
               <div className="flex gap-2 mt-2">
                 {[
@@ -405,6 +438,7 @@ export function CreateTimerModal({ isOpen, onClose }: CreateTimerModalProps) {
                   color: 'var(--cm-text-primary)',
                 }}
               />
+              {errors.eventDate && <p className="text-xs mt-1" style={{ color: 'var(--cm-danger)' }}>{errors.eventDate}</p>}
               {eventDate && new Date(eventDate).getTime() > Date.now() && (
                 <p className="text-xs mt-1" style={{ color: 'var(--cm-text-tertiary)' }}>
                   {Math.ceil((new Date(eventDate).getTime() - Date.now()) / 86_400_000)} days from now &middot; Milestone warnings at 30, 7, 3, 1 days
diff --git a/web/src/lib/schemas.ts b/web/src/lib/schemas.ts
index b9b44bc..6a7b176 100644
--- a/web/src/lib/schemas.ts
+++ b/web/src/lib/schemas.ts
@@ -29,6 +29,17 @@ export const pomodoroSchema = z.object({
   urgency: z.enum(['critical', 'important', 'standard', 'gentle', 'passive']),
 });
 
+export const eventSchema = z.object({
+  label: z.string().max(100, 'Label too long').default('Event Countdown'),
+  eventDate: z.string().min(1, 'Event date is required'),
+  urgency: z.enum(['critical', 'important', 'standard', 'gentle', 'passive']),
+  cascadePreset: z.enum(['aggressive', 'standard', 'light', 'minimal', 'none', 'custom']),
+}).refine(
+  (data) => new Date(data.eventDate).getTime() > Date.now(),
+  { message: 'Event date must be in the future', path: ['eventDate'] }
+);
+
 export type AlarmFormData = z.infer<typeof alarmSchema>;
 export type CountdownFormData = z.infer<typeof countdownSchema>;
 export type PomodoroFormData = z.infer<typeof pomodoroSchema>;
+export type EventFormData = z.infer<typeof eventSchema>;