diff --git a/apps/client/src/shared/components/optionsMenuButton/OptionsMenuButton.tsx b/apps/client/src/shared/components/optionsMenuButton/OptionsMenuButton.tsx
index 9c7ddc86..ab30056e 100644
--- a/apps/client/src/shared/components/optionsMenuButton/OptionsMenuButton.tsx
+++ b/apps/client/src/shared/components/optionsMenuButton/OptionsMenuButton.tsx
@@ -9,7 +9,7 @@ export interface OptionsMenuButtonProps {
 
 const ITEM_STYLE =
   'body4-r text-font-black-1 h-[3.6rem] w-full ' +
-  'flex items-center pl-[0.8rem] ' +
+  'flex items-center justify-center ' +
   'hover:bg-gray100 focus-visible:bg-gray100 active:bg-gray200 ' +
   'outline-none transition-colors';
 
diff --git a/apps/client/src/shared/components/sidebar/PopupPortal.tsx b/apps/client/src/shared/components/sidebar/PopupPortal.tsx
index a5e30df1..636ba598 100644
--- a/apps/client/src/shared/components/sidebar/PopupPortal.tsx
+++ b/apps/client/src/shared/components/sidebar/PopupPortal.tsx
@@ -1,16 +1,24 @@
 import { createPortal } from 'react-dom';
-import { Popup } from '@pinback/design-system/ui';
+import { useEffect, useState } from 'react';
+import { AutoDismissToast, Popup, Toast } from '@pinback/design-system/ui';
 import type { PopupState } from '@shared/hooks/useCategoryPopups';
 
 interface Props {
-  popup: PopupState;
+  popup: PopupState | null;
   onClose: () => void;
   onChange?: (value: string) => void;
   onCreateConfirm?: () => void;
   onEditConfirm?: (id: number, draft?: string) => void;
   onDeleteConfirm?: (id: number) => void;
+  categoryList?: { id: number; name: string }[];
+  isToastOpen?: boolean;
+  onToastClose?: () => void;
+  toastKey?: number;
+  toastAction?: 'create' | 'edit' | 'delete';
 }
 
+const MAX_LEN = 10;
+
 export default function PopupPortal({
   popup,
   onClose,
@@ -18,9 +26,74 @@ export default function PopupPortal({
   onCreateConfirm,
   onEditConfirm,
   onDeleteConfirm,
+  categoryList,
+  isToastOpen,
+  onToastClose,
+  toastKey,
+  toastAction,
 }: Props) {
+  const [draft, setDraft] = useState('');
+
+  useEffect(() => {
+    if (!popup) return;
+    setDraft(popup.kind === 'edit' ? (popup.name ?? '') : '');
+  }, [popup]);
+
   if (!popup) return null;
 
+  const value = draft.trim();
+  const len = value.length;
+
+  const isEmpty = popup.kind !== 'delete' && len === 0;
+  const isDuplicate =
+    popup.kind !== 'delete' &&
+    !!categoryList?.some(
+      (c) => c.name === value && (popup.kind === 'create' || c.id !== popup.id)
+    );
+
+  let helperText = '';
+  let isErrorUI = false;
+
+  if (!isEmpty && popup.kind !== 'delete') {
+    if (isDuplicate) {
+      helperText = '이미 존재하는 카테고리 이름입니다.';
+      isErrorUI = true;
+    } else if (len > MAX_LEN) {
+      helperText = `카테고리 이름은 ${MAX_LEN}자 이내로 입력해주세요.`;
+      isErrorUI = true;
+    } else if (len === MAX_LEN) {
+      helperText = `최대 ${MAX_LEN}자까지 입력할 수 있어요.`;
+      isErrorUI = false;
+    }
+  }
+
+  const handleInputChange = (next: string) => {
+    setDraft(next);
+    onChange?.(next);
+  };
+
+  const blocked =
+    popup.kind !== 'delete' && (isEmpty || isDuplicate || len > MAX_LEN);
+
+  const handleCreate = () => {
+    if (blocked) return;
+    onCreateConfirm?.();
+  };
+
+  const handleEdit = () => {
+    if (blocked || popup.kind !== 'edit') return;
+    onEditConfirm?.(popup.id, value);
+  };
+
+  const handleDelete = () => {
+    if (popup.kind !== 'delete') return;
+    onDeleteConfirm?.(popup.id);
+  };
+
+  const action = toastAction ?? (popup.kind as 'create' | 'edit' | 'delete');
+  const actionLabel =
+    action === 'create' ? '추가' : action === 'edit' ? '수정' : '삭제';
+
   return createPortal(
     <div className="fixed inset-0 z-[11000]">
       <div className="absolute inset-0 bg-black/60" onClick={onClose} />
@@ -31,10 +104,13 @@ export default function PopupPortal({
             title="카테고리 추가하기"
             left="취소"
             right="추가"
-            onInputChange={onChange}
+            isError={isErrorUI}
+            helperText={helperText}
+            inputValue={draft}
+            onInputChange={handleInputChange}
             placeholder="카테고리 제목을 입력해주세요"
             onLeftClick={onClose}
-            onRightClick={() => onCreateConfirm?.()}
+            onRightClick={handleCreate}
           />
         )}
 
@@ -44,10 +120,12 @@ export default function PopupPortal({
             title="카테고리 수정하기"
             left="취소"
             right="확인"
-            onInputChange={onChange}
-            defaultValue={popup.name}
+            isError={isErrorUI}
+            helperText={helperText}
+            inputValue={draft}
+            onInputChange={handleInputChange}
             onLeftClick={onClose}
-            onRightClick={() => onEditConfirm?.(popup.id)}
+            onRightClick={handleEdit}
           />
         )}
 
@@ -59,9 +137,22 @@ export default function PopupPortal({
             left="취소"
             right="삭제"
             onLeftClick={onClose}
-            onRightClick={() => onDeleteConfirm?.(popup.id)}
+            onRightClick={handleDelete}
           />
         )}
+
+        {isToastOpen && (
+          <div className="absolute bottom-[23.4rem] left-1/2 -translate-x-1/2">
+            <AutoDismissToast
+              key={toastKey}
+              duration={1000}
+              fadeMs={500}
+              onClose={onToastClose}
+            >
+              <Toast text={`${actionLabel}에 실패했어요.\n다시 시도해주세요`} />
+            </AutoDismissToast>
+          </div>
+        )}
       </div>
     </div>,
     document.body
diff --git a/apps/client/src/shared/components/sidebar/Sidebar.tsx b/apps/client/src/shared/components/sidebar/Sidebar.tsx
index 103cfa33..d9ccc71f 100644
--- a/apps/client/src/shared/components/sidebar/Sidebar.tsx
+++ b/apps/client/src/shared/components/sidebar/Sidebar.tsx
@@ -17,11 +17,13 @@ import {
   usePutCategory,
   useDeleteCategory,
 } from '@shared/apis/queries';
-import { useState } from 'react';
+import { useEffect, useState } from 'react';
 import { useQueryClient } from '@tanstack/react-query';
 
 export function Sidebar() {
   const [newCategoryName, setNewCategoryName] = useState('');
+  const [toastIsOpen, setToastIsOpen] = useState(false);
+
   const queryClient = useQueryClient();
 
   const { data: categories } = useGetDashboardCategories();
@@ -58,6 +60,10 @@ export function Sidebar() {
     setNewCategoryName(name);
   };
 
+  useEffect(() => {
+    setToastIsOpen(false);
+  }, [popup]);
+
   const handleCreateCategory = () => {
     createCategory(newCategoryName, {
       onSuccess: () => {
@@ -65,11 +71,12 @@ export function Sidebar() {
         queryClient.invalidateQueries({ queryKey: ['dashboardCategories'] });
         close();
       },
-      onError: (error) => {
-        console.error('카테고리 생성 실패:', error);
+      onError: () => {
+        setToastIsOpen(true);
       },
     });
   };
+
   const handlePatchCategory = (id: number) => {
     patchCategory(
       { id, categoryName: newCategoryName },
@@ -79,7 +86,9 @@ export function Sidebar() {
           queryClient.invalidateQueries({ queryKey: ['dashboardCategories'] });
           close();
         },
-        onError: (error) => console.error('카테고리 수정 실패:', error),
+        onError: () => {
+          setToastIsOpen(true);
+        },
       }
     );
   };
@@ -90,12 +99,17 @@ export function Sidebar() {
         queryClient.invalidateQueries({ queryKey: ['dashboardCategories'] });
         close();
       },
-      onError: (error) => {
-        console.error('카테고리 삭제 실패:', error);
+      onError: () => {
+        setToastIsOpen(true);
       },
     });
   };
 
+  const handlePopupClose = () => {
+    setToastIsOpen(false);
+    close();
+  };
+
   if (isPending) return <div></div>;
   if (isError) return <div></div>;
   const acornCount = data.acornCount;
@@ -149,7 +163,12 @@ export function Sidebar() {
                 />
               ))}
 
-              <CreateItem onClick={openCreate} />
+              <CreateItem
+                onClick={() => {
+                  setToastIsOpen(false);
+                  openCreate();
+                }}
+              />
             </ul>
           </AccordionItem>
 
@@ -158,8 +177,14 @@ export function Sidebar() {
             style={style ?? undefined}
             categoryId={menu.categoryId}
             getCategoryName={getCategoryName}
-            onEdit={(id, name) => openEdit(id, name)}
-            onDelete={(id, name) => openDelete(id, name)}
+            onEdit={(id, name) => {
+              setToastIsOpen(false);
+              openEdit(id, name);
+            }}
+            onDelete={(id, name) => {
+              setToastIsOpen(false);
+              openDelete(id, name);
+            }}
             onClose={closeMenu}
             containerRef={containerRef}
           />
@@ -180,11 +205,14 @@ export function Sidebar() {
 
       <PopupPortal
         popup={popup}
-        onClose={close}
+        onClose={handlePopupClose}
         onChange={handleCategoryChange}
         onCreateConfirm={handleCreateCategory}
         onEditConfirm={(id) => handlePatchCategory(id)}
         onDeleteConfirm={(id) => handleDeleteCategory(id)}
+        categoryList={categories?.categories ?? []}
+        isToastOpen={toastIsOpen}
+        onToastClose={() => setToastIsOpen(false)}
       />
     </aside>
   );