diff --git a/web/chat/thread-menu.react.js b/web/chat/thread-menu.react.js
index e7cdcc3f8..d64483960 100644
--- a/web/chat/thread-menu.react.js
+++ b/web/chat/thread-menu.react.js
@@ -1,250 +1,263 @@
 // @flow
 
 import * as React from 'react';
 
 import {
   leaveThread,
   leaveThreadActionTypes,
 } from 'lib/actions/thread-actions';
 import { usePromoteSidebar } from 'lib/hooks/promote-sidebar.react';
 import { childThreadInfos } from 'lib/selectors/thread-selectors';
 import {
   threadHasPermission,
   viewerIsMember,
   threadIsChannel,
 } from 'lib/shared/thread-utils';
 import {
   type ThreadInfo,
   threadTypes,
   threadPermissions,
 } from 'lib/types/thread-types';
 import {
   useServerCall,
   useDispatchActionPromise,
 } from 'lib/utils/action-utils';
 import { isDev } from 'lib/utils/dev-utils';
 
 import MenuItem from '../components/menu-item.react';
 import Menu from '../components/menu.react';
 import SidebarListModal from '../modals/chat/sidebar-list-modal.react';
+import SidebarPromoteModal from '../modals/chat/sidebar-promote-modal.react';
 import { useModalContext } from '../modals/modal-provider.react';
 import ConfirmLeaveThreadModal from '../modals/threads/confirm-leave-thread-modal.react';
 import ThreadMembersModal from '../modals/threads/members/members-modal.react';
 import SubchannelsModal from '../modals/threads/subchannels/subchannels-modal.react';
 import ThreadSettingsModal from '../modals/threads/thread-settings-modal.react';
 import { useSelector } from '../redux/redux-utils';
 import SWMansionIcon from '../SWMansionIcon.react';
 import css from './thread-menu.css';
 
 type ThreadMenuProps = {
   +threadInfo: ThreadInfo,
 };
 
 function ThreadMenu(props: ThreadMenuProps): React.Node {
   const { pushModal, popModal } = useModalContext();
   const { threadInfo } = props;
   const { onPromoteSidebar } = usePromoteSidebar(threadInfo);
 
   const onClickSettings = React.useCallback(
     () => pushModal(<ThreadSettingsModal threadID={threadInfo.id} />),
     [pushModal, threadInfo.id],
   );
 
   const settingsItem = React.useMemo(() => {
     return (
       <MenuItem
         key="settings"
         text="Settings"
         icon="wrench"
         onClick={onClickSettings}
       />
     );
   }, [onClickSettings]);
 
   const onClickMembers = React.useCallback(
     () =>
       pushModal(
         <ThreadMembersModal threadID={threadInfo.id} onClose={popModal} />,
       ),
     [popModal, pushModal, threadInfo.id],
   );
   const membersItem = React.useMemo(() => {
     if (threadInfo.type === threadTypes.PERSONAL) {
       return null;
     }
     return (
       <MenuItem
         key="members"
         text="Members"
         icon="users"
         onClick={onClickMembers}
       />
     );
   }, [onClickMembers, threadInfo.type]);
 
   const childThreads = useSelector(
     state => childThreadInfos(state)[threadInfo.id],
   );
 
   const hasSidebars = React.useMemo(() => {
     return childThreads?.some(
       childThreadInfo => childThreadInfo.type === threadTypes.SIDEBAR,
     );
   }, [childThreads]);
 
   const onClickSidebars = React.useCallback(
     () => pushModal(<SidebarListModal threadInfo={threadInfo} />),
     [pushModal, threadInfo],
   );
 
   const sidebarItem = React.useMemo(() => {
     if (!hasSidebars) {
       return null;
     }
     return (
       <MenuItem
         key="sidebars"
         text="Sidebars"
         icon="arrow-right-small"
         onClick={onClickSidebars}
       />
     );
   }, [hasSidebars, onClickSidebars]);
 
   const canCreateSubchannels = React.useMemo(
     () => threadHasPermission(threadInfo, threadPermissions.CREATE_SUBCHANNELS),
     [threadInfo],
   );
 
   const hasSubchannels = React.useMemo(() => {
     return !!childThreads?.some(threadIsChannel);
   }, [childThreads]);
 
   const onClickViewSubchannels = React.useCallback(
     () =>
       pushModal(
         <SubchannelsModal threadID={threadInfo.id} onClose={popModal} />,
       ),
     [popModal, pushModal, threadInfo.id],
   );
 
   const viewSubchannelsItem = React.useMemo(() => {
     if (!hasSubchannels) {
       return null;
     }
     return (
       <MenuItem
         key="subchannels"
         text="Subchannels"
         icon="message-square"
         onClick={onClickViewSubchannels}
       />
     );
   }, [hasSubchannels, onClickViewSubchannels]);
 
   const createSubchannelsItem = React.useMemo(() => {
     if (!canCreateSubchannels) {
       return null;
     }
     return (
       <MenuItem
         key="newSubchannel"
         text="Create new subchannel"
         icon="plus-circle"
       />
     );
   }, [canCreateSubchannels]);
 
   const dispatchActionPromise = useDispatchActionPromise();
   const callLeaveThread = useServerCall(leaveThread);
 
   const onConfirmLeaveThread = React.useCallback(() => {
     dispatchActionPromise(
       leaveThreadActionTypes,
       callLeaveThread(threadInfo.id),
     );
     popModal();
   }, [callLeaveThread, popModal, dispatchActionPromise, threadInfo.id]);
 
   const onClickLeaveThread = React.useCallback(
     () =>
       pushModal(
         <ConfirmLeaveThreadModal
           threadInfo={threadInfo}
           onClose={popModal}
           onConfirm={onConfirmLeaveThread}
         />,
       ),
     [popModal, onConfirmLeaveThread, pushModal, threadInfo],
   );
 
   const leaveThreadItem = React.useMemo(() => {
     const canLeaveThread = threadHasPermission(
       threadInfo,
       threadPermissions.LEAVE_THREAD,
     );
     if (!viewerIsMember(threadInfo) || !canLeaveThread) {
       return null;
     }
     return (
       <MenuItem
         key="leave"
         text="Leave Thread"
         icon="logout"
         dangerous
         onClick={onClickLeaveThread}
       />
     );
   }, [onClickLeaveThread, threadInfo]);
 
+  const onClickPromoteSidebarToThread = React.useCallback(
+    () =>
+      pushModal(
+        <SidebarPromoteModal
+          threadInfo={threadInfo}
+          onClose={popModal}
+          onConfirm={onPromoteSidebar}
+        />,
+      ),
+    [pushModal, threadInfo, popModal, onPromoteSidebar],
+  );
+
   const promoteSidebar = React.useMemo(() => {
     return (
       <MenuItem
         key="promote"
         text="Promote Thread"
         icon="message-square-lines"
-        onClick={onPromoteSidebar}
+        onClick={onClickPromoteSidebarToThread}
       />
     );
-  }, [onPromoteSidebar]);
+  }, [onClickPromoteSidebarToThread]);
 
   const menuItems = React.useMemo(() => {
     const notificationsItem = (
       <MenuItem key="notifications" text="Notifications" icon="bell" />
     );
     const separator = <hr key="separator" className={css.separator} />;
 
     // TODO: Enable menu items when the modals are implemented
     const SHOW_NOTIFICATIONS = false;
     const SHOW_CREATE_SUBCHANNELS = false;
     const SHOW_PROMOTE_SIDEBAR = isDev;
 
     const items = [
       settingsItem,
       SHOW_NOTIFICATIONS && notificationsItem,
       membersItem,
       sidebarItem,
       viewSubchannelsItem,
       SHOW_CREATE_SUBCHANNELS && createSubchannelsItem,
       leaveThreadItem && separator,
       SHOW_PROMOTE_SIDEBAR && promoteSidebar,
       leaveThreadItem,
     ];
     return items.filter(Boolean);
   }, [
     settingsItem,
     membersItem,
     sidebarItem,
     viewSubchannelsItem,
     promoteSidebar,
     createSubchannelsItem,
     leaveThreadItem,
   ]);
   const icon = React.useMemo(
     () => <SWMansionIcon icon="menu-vertical" size={20} />,
     [],
   );
   return <Menu icon={icon}>{menuItems}</Menu>;
 }
 
 export default ThreadMenu;
diff --git a/web/modals/chat/sidebar-promote-modal.css b/web/modals/chat/sidebar-promote-modal.css
new file mode 100644
index 000000000..3dca55379
--- /dev/null
+++ b/web/modals/chat/sidebar-promote-modal.css
@@ -0,0 +1,16 @@
+div.modal_body {
+  padding: 20px;
+  color: var(--fg);
+  background-color: var(--modal-bg);
+  border-radius: 16px;
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+}
+
+div.buttonContainer {
+  padding-top: 32px;
+  display: flex;
+  gap: 24px;
+  justify-content: flex-end;
+}
diff --git a/web/modals/chat/sidebar-promote-modal.react.js b/web/modals/chat/sidebar-promote-modal.react.js
new file mode 100644
index 000000000..9268e37d1
--- /dev/null
+++ b/web/modals/chat/sidebar-promote-modal.react.js
@@ -0,0 +1,49 @@
+// @flow
+
+import * as React from 'react';
+
+import type { ThreadInfo } from 'lib/types/thread-types';
+
+import Button from '../../components/button.react';
+import Modal from '../modal.react';
+import css from './sidebar-promote-modal.css';
+
+type Props = {
+  +onClose: () => void,
+  +onConfirm: () => void,
+  +threadInfo: ThreadInfo,
+};
+
+function SidebarPromoteModal(props: Props): React.Node {
+  const { threadInfo, onClose, onConfirm } = props;
+  const { uiName } = threadInfo;
+
+  const handleConfirm = React.useCallback(() => {
+    onConfirm();
+    onClose();
+  }, [onClose, onConfirm]);
+
+  return (
+    <Modal
+      size="large"
+      name="Promote Thread"
+      icon="warning-circle"
+      onClose={onClose}
+    >
+      <div className={css.modal_body}>
+        <p>{`Are you sure you want to promote "${uiName}"?`}</p>
+        <p>Promoting a sidebar to a full thread cannot be undone.</p>
+        <div className={css.buttonContainer}>
+          <Button onClick={onClose} type="submit" variant="secondary">
+            Cancel
+          </Button>
+          <Button onClick={handleConfirm} type="submit" variant="danger">
+            Promote to Full Thread
+          </Button>
+        </div>
+      </div>
+    </Modal>
+  );
+}
+
+export default SidebarPromoteModal;