diff --git a/frontend/app/(main)/mail/imap/page.tsx b/frontend/app/(main)/mail/imap/page.tsx
index 4dc6362f..ccdeb317 100644
--- a/frontend/app/(main)/mail/imap/page.tsx
+++ b/frontend/app/(main)/mail/imap/page.tsx
@@ -129,6 +129,7 @@ export default function ImapMailPage() {
   const [searchTerm, setSearchTerm] = useState("");
   const [saving, setSaving] = useState(false);
   const [saveError, setSaveError] = useState<string | null>(null);
+  const [formErrors, setFormErrors] = useState<Partial<Record<'displayName' | 'email' | 'host' | 'username' | 'password', string>>>({});
 
   // New states
   const [folders, setFolders] = useState<MailFolder[]>([]);
@@ -432,6 +433,7 @@ export default function ImapMailPage() {
     setTestResult(null);
     setShowPassword(false);
     setHostPopoverOpen(false);
+    setFormErrors({});
     setShowDialog(true);
   }
 
@@ -461,6 +463,14 @@ export default function ImapMailPage() {
   }
 
   async function handleSave() {
+    const errors: typeof formErrors = {};
+    if (!form.displayName.trim()) errors.displayName = "표시 이름을 입력하세요.";
+    if (!form.email.trim()) errors.email = "이메일 주소를 입력하세요.";
+    if (!form.host.trim()) errors.host = "IMAP 호스트를 입력하세요.";
+    if (!form.username.trim()) errors.username = "사용자명을 입력하세요.";
+    if (!editingAccount && !form.password.trim()) errors.password = "비밀번호를 입력하세요.";
+    if (Object.keys(errors).length > 0) { setFormErrors(errors); return; }
+    setFormErrors({});
     setSaving(true);
     setSaveError(null);
     try {
@@ -914,18 +924,22 @@ export default function ImapMailPage() {
               <Label className="text-xs">표시 이름</Label>
               <Input
                 value={form.displayName}
-                onChange={(e) => setForm((p) => ({ ...p, displayName: e.target.value }))}
+                onChange={(e) => { setForm((p) => ({ ...p, displayName: e.target.value })); setFormErrors((p) => ({ ...p, displayName: undefined })); }}
                 placeholder="내 Gmail"
+                className={formErrors.displayName ? "border-destructive" : ""}
               />
+              {formErrors.displayName && <p className="text-xs text-destructive">{formErrors.displayName}</p>}
             </div>
             <div className="space-y-1">
               <Label className="text-xs">이메일 주소</Label>
               <Input
                 type="email"
                 value={form.email}
-                onChange={(e) => setForm((p) => ({ ...p, email: e.target.value, username: e.target.value }))}
+                onChange={(e) => { setForm((p) => ({ ...p, email: e.target.value, username: e.target.value })); setFormErrors((p) => ({ ...p, email: undefined })); }}
                 placeholder="user@example.com"
+                className={formErrors.email ? "border-destructive" : ""}
               />
+              {formErrors.email && <p className="text-xs text-destructive">{formErrors.email}</p>}
             </div>
             <div className="grid grid-cols-2 gap-3">
               <div className="space-y-1">
@@ -944,7 +958,7 @@ export default function ImapMailPage() {
                       <CommandInput
                         placeholder="호스트 직접 입력..."
                         value={form.host}
-                        onValueChange={(v) => setForm((p) => ({ ...p, host: v }))}
+                        onValueChange={(v) => { setForm((p) => ({ ...p, host: v })); setFormErrors((p) => ({ ...p, host: undefined })); }}
                       />
                       <CommandList>
                         <CommandEmpty>직접 입력한 값을 사용합니다</CommandEmpty>
@@ -970,6 +984,7 @@ export default function ImapMailPage() {
                     </Command>
                   </PopoverContent>
                 </Popover>
+              {formErrors.host && <p className="text-xs text-destructive">{formErrors.host}</p>}
               </div>
               <div className="space-y-1">
                 <Label className="text-xs">포트</Label>
@@ -988,9 +1003,11 @@ export default function ImapMailPage() {
               <Label className="text-xs">사용자명</Label>
               <Input
                 value={form.username}
-                onChange={(e) => setForm((p) => ({ ...p, username: e.target.value }))}
+                onChange={(e) => { setForm((p) => ({ ...p, username: e.target.value })); setFormErrors((p) => ({ ...p, username: undefined })); }}
                 placeholder="user@example.com"
+                className={formErrors.username ? "border-destructive" : ""}
               />
+              {formErrors.username && <p className="text-xs text-destructive">{formErrors.username}</p>}
             </div>
             <div className="space-y-1">
               <Label className="text-xs">비밀번호 {editingAccount && "(변경 시에만 입력)"}</Label>
@@ -998,10 +1015,10 @@ export default function ImapMailPage() {
                 <Input
                   type={showPassword ? "text" : "password"}
                   value={form.password}
-                  onChange={(e) => setForm((p) => ({ ...p, password: e.target.value }))}
+                  onChange={(e) => { setForm((p) => ({ ...p, password: e.target.value })); setFormErrors((p) => ({ ...p, password: undefined })); }}
                   onKeyDown={(e) => { if (e.key === "Enter") handleSave(); }}
                   placeholder="••••••••"
-                  className="pr-9"
+                  className={`pr-9 ${formErrors.password ? "border-destructive" : ""}`}
                 />
                 <button
                   type="button"
@@ -1011,6 +1028,7 @@ export default function ImapMailPage() {
                   {showPassword ? <EyeOff className="h-4 w-4" /> : <Eye className="h-4 w-4" />}
                 </button>
               </div>
+              {formErrors.password && <p className="text-xs text-destructive">{formErrors.password}</p>}
             </div>
             {editingAccount && (
               <div>