diff --git a/src/__test__/integration/ui/toolbar.spec.ts b/src/__test__/integration/ui/toolbar.spec.ts
index 0e36d6fe8d..3162958730 100644
--- a/src/__test__/integration/ui/toolbar.spec.ts
+++ b/src/__test__/integration/ui/toolbar.spec.ts
@@ -493,6 +493,8 @@ describe('custom button toolbar', () => {
 });
 
 describe('custom toolbar element', () => {
+  const onUpdatedSpy = jest.fn();
+
   function createCustomItem() {
     const el = document.createElement('div');
 
@@ -503,6 +505,8 @@ describe('custom toolbar element', () => {
       el,
       name: 'myToolbar',
       tooltip: 'custom1!',
+      state: 'strong',
+      onUpdated: onUpdatedSpy,
     };
   }
 
@@ -541,6 +545,14 @@ describe('custom toolbar element', () => {
     };
   }
 
+  function clickMarkdownWriteTab() {
+    document.querySelectorAll<HTMLElement>('.tab-item')![0].click();
+  }
+
+  function clickMarkdownPreviewTab() {
+    document.querySelectorAll<HTMLElement>('.tab-item')![1].click();
+  }
+
   const customItem = createCustomItem();
   const customItemWithPopup = createCustomItemWithPopup();
 
@@ -550,6 +562,7 @@ describe('custom toolbar element', () => {
     container = document.createElement('div');
     document.body.appendChild(container);
 
+    onUpdatedSpy.mockReset();
     em = new EventEmitter();
 
     destroy = render(
@@ -557,7 +570,7 @@ describe('custom toolbar element', () => {
       html`
         <${Toolbar}
           eventEmitter=${em}
-          previewStyle="vertical"
+          previewStyle="tab"
           toolbarItems=${toolbarItems}
           editorType="markdown"
         />
@@ -605,6 +618,30 @@ describe('custom toolbar element', () => {
 
     expect(spy).toHaveBeenCalledWith('heading', { level: 3 });
   });
+
+  it('should toggle active state properly when toolbar state is changed', () => {
+    em.emit('changeToolbarState', { toolbarState: { strong: true } });
+
+    expect(onUpdatedSpy).toHaveBeenCalledWith(expect.objectContaining({ active: true }));
+
+    em.emit('changeToolbarState', { toolbarState: { strong: false } });
+
+    expect(onUpdatedSpy).toHaveBeenCalledWith(expect.objectContaining({ active: false }));
+  });
+
+  it('should toggle disabled state when changing markdown tab mode', () => {
+    em.emit('changePreviewStyle', 'tab');
+
+    // change markdown tab mode to preview tab
+    clickMarkdownPreviewTab();
+
+    expect(onUpdatedSpy).toHaveBeenCalledWith(expect.objectContaining({ disabled: true }));
+
+    // change markdown tab mode to write tab
+    clickMarkdownWriteTab();
+
+    expect(onUpdatedSpy).toHaveBeenCalledWith(expect.objectContaining({ disabled: false }));
+  });
 });
 
 describe('API', () => {
diff --git a/src/css/editor.css b/src/css/editor.css
index 9c8607e217..1b39db4ce5 100644
--- a/src/css/editor.css
+++ b/src/css/editor.css
@@ -405,7 +405,7 @@
   display: flex;
 }
 
-.tui-toolbar-item-wrapper {
+.toastui-editor-toolbar-item-wrapper {
   margin: 7px 5px;
   height: 32px;
   line-height: 32px;
diff --git a/src/ui/components/layout.ts b/src/ui/components/layout.ts
index 764f453ae9..efbaf04fe8 100644
--- a/src/ui/components/layout.ts
+++ b/src/ui/components/layout.ts
@@ -63,9 +63,9 @@ export class Layout extends Component<Props, State> {
     const { eventEmitter, hideModeSwitch, toolbarItems, theme } = this.props;
     const { hide, previewStyle, editorType } = this.state;
     const displayClassName = hide ? ' hidden' : '';
-    const editorTypeClassName = editorType === 'markdown' ? cls('md-mode') : cls('ww-mode');
+    const editorTypeClassName = cls(editorType === 'markdown' ? 'md-mode' : 'ww-mode');
     const previewClassName = `${cls('md')}-${previewStyle}-style`;
-    const themeClassName = theme === 'light' ? '' : `${cls(theme)} `;
+    const themeClassName = cls([theme !== 'light', `${theme} `]);
 
     return html`
       <div
diff --git a/src/ui/components/toolbar/buttonHoc.ts b/src/ui/components/toolbar/buttonHoc.ts
index 1438135935..167724437c 100644
--- a/src/ui/components/toolbar/buttonHoc.ts
+++ b/src/ui/components/toolbar/buttonHoc.ts
@@ -6,6 +6,7 @@ import {
   SetItemWidth,
   ComponentClass,
   ToolbarButtonInfo,
+  ToolbarState,
 } from '@t/ui';
 import { Emitter } from '@t/event';
 import html from '@/ui/vdom/template';
@@ -22,10 +23,36 @@ interface Props {
   setItemWidth?: SetItemWidth;
 }
 
+interface Payload {
+  toolbarState: ToolbarState;
+}
+
+interface State {
+  active: boolean;
+}
+
 const TOOLTIP_INDENT = 6;
 
 export function connectHOC(WrappedComponent: ComponentClass) {
-  return class ButtonHOC extends Component<Props> {
+  return class ButtonHOC extends Component<Props, State> {
+    constructor(props: Props) {
+      super(props);
+      this.state = { active: false };
+      this.addEvent();
+    }
+
+    private addEvent() {
+      const { item, eventEmitter } = this.props;
+
+      if (item.state) {
+        eventEmitter.listen('changeToolbarState', ({ toolbarState }: Payload) => {
+          const active = !!toolbarState[item.state!];
+
+          this.setState({ active });
+        });
+      }
+    }
+
     private getBound(el: HTMLElement) {
       const { offsetLeft, offsetTop } = getTotalOffset(
         el,
@@ -56,6 +83,7 @@ export function connectHOC(WrappedComponent: ComponentClass) {
       return html`
         <${WrappedComponent}
           ...${this.props}
+          active=${this.state.active}
           showTooltip=${this.showTooltip}
           hideTooltip=${this.hideTooltip}
           getBound=${this.getBound}
diff --git a/src/ui/components/toolbar/customToolbarItem.ts b/src/ui/components/toolbar/customToolbarItem.ts
index 97a51c638f..44921d009a 100644
--- a/src/ui/components/toolbar/customToolbarItem.ts
+++ b/src/ui/components/toolbar/customToolbarItem.ts
@@ -10,7 +10,7 @@ import {
 import { Emitter } from '@t/event';
 import html from '@/ui/vdom/template';
 import { Component } from '@/ui/vdom/component';
-import { getOuterWidth } from '@/utils/dom';
+import { cls, getOuterWidth } from '@/utils/dom';
 import { createPopupInfo } from '@/ui/toolbarItemFactory';
 import { connectHOC } from './buttonHoc';
 
@@ -18,6 +18,7 @@ interface Props {
   disabled: boolean;
   eventEmitter: Emitter;
   item: ToolbarCustomOptions;
+  active: boolean;
   execCommand: ExecCommand;
   setPopupInfo: SetPopupInfo;
   showTooltip: ShowTooltip;
@@ -42,6 +43,14 @@ class CustomToolbarItemComp extends Component<Props> {
     }
   }
 
+  updated(prevProps: Props) {
+    const { item, active, disabled } = this.props;
+
+    if (prevProps.active !== active || prevProps.disabled !== disabled) {
+      item.onUpdated?.({ active, disabled });
+    }
+  }
+
   private showTooltip = () => {
     this.props.showTooltip(this.refs.el);
   };
@@ -59,16 +68,18 @@ class CustomToolbarItemComp extends Component<Props> {
   };
 
   render() {
-    const style = { display: this.props.item.hidden ? 'none' : 'inline-block' };
+    const { disabled, item } = this.props;
+    const style = { display: item.hidden ? 'none' : 'inline-block' };
+    const getListener = (listener: Function) => (disabled ? null : listener);
 
     return html`
       <div
         ref=${(el: HTMLElement) => (this.refs.el = el)}
         style=${style}
-        class="tui-toolbar-item-wrapper"
-        onClick=${this.showPopup}
-        onMouseover=${this.showTooltip}
-        onMouseout=${this.props.hideTooltip}
+        class=${cls('toolbar-item-wrapper')}
+        onClick=${getListener(this.showPopup)}
+        onMouseover=${getListener(this.showTooltip)}
+        onMouseout=${getListener(this.props.hideTooltip)}
       ></div>
     `;
   }
diff --git a/src/ui/components/toolbar/toolbarButton.ts b/src/ui/components/toolbar/toolbarButton.ts
index 724ee9ade7..26cc421d95 100644
--- a/src/ui/components/toolbar/toolbarButton.ts
+++ b/src/ui/components/toolbar/toolbarButton.ts
@@ -1,7 +1,6 @@
 import {
   ExecCommand,
   SetPopupInfo,
-  ToolbarState,
   SetItemWidth,
   GetBound,
   HideTooltip,
@@ -15,14 +14,11 @@ import { createPopupInfo } from '@/ui/toolbarItemFactory';
 import { getOuterWidth } from '@/utils/dom';
 import { connectHOC } from './buttonHoc';
 
-interface Payload {
-  toolbarState: ToolbarState;
-}
-
 interface Props {
   disabled: boolean;
   eventEmitter: Emitter;
   item: ToolbarButtonInfo;
+  active: boolean;
   execCommand: ExecCommand;
   setPopupInfo: SetPopupInfo;
   showTooltip: ShowTooltip;
@@ -31,29 +27,9 @@ interface Props {
   setItemWidth?: SetItemWidth;
 }
 
-interface State {
-  active: boolean;
-}
-
 const DEFAULT_WIDTH = 80;
 
-export class ToolbarButtonComp extends Component<Props, State> {
-  constructor(props: Props) {
-    super(props);
-    this.state = { active: false };
-    this.addEvent();
-  }
-
-  addEvent() {
-    if (this.props.item.state) {
-      this.props.eventEmitter.listen('changeToolbarState', ({ toolbarState }: Payload) => {
-        const active = !!toolbarState[this.props.item.state!];
-
-        this.setState({ active });
-      });
-    }
-  }
-
+export class ToolbarButtonComp extends Component<Props> {
   mounted() {
     this.setItemWidth();
   }
@@ -98,9 +74,9 @@ export class ToolbarButtonComp extends Component<Props, State> {
   };
 
   render() {
-    const { hideTooltip, disabled, item } = this.props;
+    const { hideTooltip, disabled, item, active } = this.props;
     const style = { display: item.hidden ? 'none' : null, ...item.style };
-    const classNames = `${item.className || ''}${this.state.active ? ' active' : ''}`;
+    const classNames = `${item.className || ''}${active ? ' active' : ''}`;
 
     return html`
       <button
diff --git a/src/utils/dom.ts b/src/utils/dom.ts
index 877d53d760..57f5f798ab 100644
--- a/src/utils/dom.ts
+++ b/src/utils/dom.ts
@@ -20,8 +20,24 @@ export function isPositionInBox(style: CSSStyleDeclaration, offsetX: number, off
 
 const CLS_PREFIX = 'toastui-editor-';
 
-export function cls(...names: string[]) {
-  return names.map((className) => `${CLS_PREFIX}${className}`).join(' ');
+export function cls(...names: (string | [boolean, string])[]) {
+  const result = [];
+
+  for (const name of names) {
+    let className: string | null;
+
+    if (Array.isArray(name)) {
+      className = name[0] ? name[1] : null;
+    } else {
+      className = name;
+    }
+
+    if (className) {
+      result.push(`${CLS_PREFIX}${className}`);
+    }
+  }
+
+  return result.join(' ');
 }
 
 export function clsWithMdPrefix(...names: string[]) {
diff --git a/types/editor.d.ts b/types/editor.d.ts
index 329be17772..ae320ab04a 100644
--- a/types/editor.d.ts
+++ b/types/editor.d.ts
@@ -126,7 +126,7 @@ export interface EditorOptions {
   language?: string;
   useCommandShortcut?: boolean;
   usageStatistics?: boolean;
-  toolbarItems?: (string | ToolbarItemOptions)[];
+  toolbarItems?: (string | ToolbarItemOptions)[][];
   hideModeSwitch?: boolean;
   plugins?: EditorPlugin[];
   extendedAutolinks?: ExtendedAutolinks;
diff --git a/types/ui.d.ts b/types/ui.d.ts
index 399f4cf1a1..9494b8611f 100644
--- a/types/ui.d.ts
+++ b/types/ui.d.ts
@@ -12,6 +12,12 @@ export interface ToolbarButtonOptions {
   text?: string;
   style?: Record<string, any>;
   popup?: PopupOptions;
+  state?: ToolbarStateKeys;
+}
+
+interface ToolbarCustomItemState {
+  active: boolean;
+  disabled: boolean;
 }
 
 export interface ToolbarCustomOptions {
@@ -20,11 +26,12 @@ export interface ToolbarCustomOptions {
   el?: HTMLElement;
   popup?: PopupOptions;
   hidden?: boolean;
+  state?: ToolbarStateKeys;
   onMounted?: (execCommand: ExecCommand) => void;
+  onUpdated?: (toolbarState: ToolbarCustomItemState) => void;
 }
 
 export type ToolbarButtonInfo = {
-  state?: ToolbarStateKeys;
   hidden?: boolean;
 } & ToolbarButtonOptions;