diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index c88fdc28b9..7d61d0aa8b 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -4755,6 +4755,10 @@
     "message": "Block group",
     "description": "This is a button to block a group"
   },
+  "ConversationDetailsActions--leave-group-must-choose-new-admin": {
+    "message": "Before you leave, you must choose at least one new admin for this group.",
+    "description": "Shown if, before leaving a group, you need to choose an admin"
+  },
   "ConversationDetailsActions--leave-group-modal-title": {
     "message": "Do you really want to leave?",
     "description": "This is the modal title for confirming leaving a group"
diff --git a/stylesheets/_modules.scss b/stylesheets/_modules.scss
index 24cc5dd095..38587ebc99 100644
--- a/stylesheets/_modules.scss
+++ b/stylesheets/_modules.scss
@@ -2966,6 +2966,16 @@ button.module-conversation-details__action-button {
 
   &__leave-group {
     color: $color-accent-red;
+
+    &--disabled {
+      @include light-theme {
+        color: $color-gray-60;
+      }
+
+      @include dark-theme {
+        color: $color-gray-25;
+      }
+    }
   }
 
   &__block-group {
@@ -3180,6 +3190,16 @@ button.module-conversation-details__action-button {
           -webkit-mask: url(../images/icons/v2/leave-24.svg) no-repeat center;
           background-color: $color-accent-red;
         }
+
+        &--disabled::after {
+          @include light-theme {
+            background-color: $color-gray-60;
+          }
+
+          @include dark-theme {
+            background-color: $color-gray-25;
+          }
+        }
       }
 
       &--block {
@@ -3248,19 +3268,19 @@ button.module-conversation-details__action-button {
       &--button {
         color: inherit;
         background: none;
-      }
 
-      &:hover {
-        @include light-theme {
-          background-color: $color-gray-02;
-        }
+        &:hover:not(:disabled) {
+          @include light-theme {
+            background-color: $color-gray-02;
+          }
 
-        @include dark-theme {
-          background-color: $color-gray-90;
-        }
+          @include dark-theme {
+            background-color: $color-gray-90;
+          }
 
-        & .module-conversation-details-panel-row__actions {
-          opacity: 1;
+          & .module-conversation-details-panel-row__actions {
+            opacity: 1;
+          }
         }
       }
 
diff --git a/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx b/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
index 7d5327fc8d..76a66a3b8e 100644
--- a/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
@@ -25,7 +25,7 @@ const conversation: ConversationType = {
   lastUpdated: 0,
   markedUnread: false,
   memberships: Array.from(Array(32)).map((_, i) => ({
-    isAdmin: false,
+    isAdmin: i === 1,
     member: getDefaultConversation({
       isMe: i === 2,
     }),
@@ -84,6 +84,44 @@ story.add('as Admin', () => {
   return <ConversationDetails {...props} isAdmin />;
 });
 
+story.add('as last admin', () => {
+  const props = createProps();
+
+  return (
+    <ConversationDetails
+      {...props}
+      isAdmin
+      conversation={{
+        ...conversation,
+        memberships: conversation.memberships?.map(membership => ({
+          ...membership,
+          isAdmin: Boolean(membership.member.isMe),
+        })),
+      }}
+    />
+  );
+});
+
+story.add('as only admin', () => {
+  const props = createProps();
+
+  return (
+    <ConversationDetails
+      {...props}
+      isAdmin
+      conversation={{
+        ...conversation,
+        memberships: conversation.memberships
+          ?.filter(membership => membership.member.isMe)
+          .map(membership => ({
+            ...membership,
+            isAdmin: true,
+          })),
+      }}
+    />
+  );
+});
+
 story.add('Group Editable', () => {
   const props = createProps();
 
diff --git a/ts/components/conversation/conversation-details/ConversationDetails.tsx b/ts/components/conversation/conversation-details/ConversationDetails.tsx
index 6acc62bee2..3f39dfedcb 100644
--- a/ts/components/conversation/conversation-details/ConversationDetails.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetails.tsx
@@ -101,12 +101,21 @@ export const ConversationDetails: React.ComponentType<Props> = ({
     throw new Error('ConversationDetails rendered without a conversation');
   }
 
+  const memberships = conversation.memberships || [];
   const pendingMemberships = conversation.pendingMemberships || [];
   const pendingApprovalMemberships =
     conversation.pendingApprovalMemberships || [];
   const invitesCount =
     pendingMemberships.length + pendingApprovalMemberships.length;
 
+  const otherMemberships = memberships.filter(({ member }) => !member.isMe);
+  const isJustMe = otherMemberships.length === 0;
+  const isAnyoneElseAnAdmin = otherMemberships.some(
+    membership => membership.isAdmin
+  );
+  const cannotLeaveBecauseYouAreLastAdmin =
+    isAdmin && !isJustMe && !isAnyoneElseAnAdmin;
+
   let modalNode: ReactNode;
   switch (modalState) {
     case ModalState.NothingOpen:
@@ -158,11 +167,7 @@ export const ConversationDetails: React.ComponentType<Props> = ({
             });
           }}
           conversationIdsAlreadyInGroup={
-            new Set(
-              (conversation.memberships || []).map(
-                membership => membership.member.id
-              )
-            )
+            new Set(memberships.map(membership => membership.member.id))
           }
           groupTitle={conversation.title}
           i18n={i18n}
@@ -238,7 +243,7 @@ export const ConversationDetails: React.ComponentType<Props> = ({
       <ConversationDetailsMembershipList
         canAddNewMembers={canEditGroupInfo}
         i18n={i18n}
-        memberships={conversation.memberships || []}
+        memberships={memberships}
         showContactModal={showContactModal}
         startAddingNewMembers={() => {
           setModalState(ModalState.AddingGroupMembers);
@@ -294,6 +299,7 @@ export const ConversationDetails: React.ComponentType<Props> = ({
 
       <ConversationDetailsActions
         i18n={i18n}
+        cannotLeaveBecauseYouAreLastAdmin={cannotLeaveBecauseYouAreLastAdmin}
         conversationTitle={conversation.title}
         onDelete={onDelete}
         onBlockAndDelete={onBlockAndDelete}
diff --git a/ts/components/conversation/conversation-details/ConversationDetailsActions.stories.tsx b/ts/components/conversation/conversation-details/ConversationDetailsActions.stories.tsx
index 81550629da..023dbe2dda 100644
--- a/ts/components/conversation/conversation-details/ConversationDetailsActions.stories.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetailsActions.stories.tsx
@@ -1,7 +1,8 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as React from 'react';
+import { isBoolean } from 'lodash';
 
 import { storiesOf } from '@storybook/react';
 import { action } from '@storybook/addon-actions';
@@ -21,6 +22,11 @@ const story = storiesOf(
 );
 
 const createProps = (overrideProps: Partial<Props> = {}): Props => ({
+  cannotLeaveBecauseYouAreLastAdmin: isBoolean(
+    overrideProps.cannotLeaveBecauseYouAreLastAdmin
+  )
+    ? overrideProps.cannotLeaveBecauseYouAreLastAdmin
+    : false,
   conversationTitle: overrideProps.conversationTitle || '',
   onBlockAndDelete: action('onBlockAndDelete'),
   onDelete: action('onDelete'),
@@ -32,3 +38,9 @@ story.add('Basic', () => {
 
   return <ConversationDetailsActions {...props} />;
 });
+
+story.add('Cannot leave because you are the last admin', () => {
+  const props = createProps({ cannotLeaveBecauseYouAreLastAdmin: true });
+
+  return <ConversationDetailsActions {...props} />;
+});
diff --git a/ts/components/conversation/conversation-details/ConversationDetailsActions.tsx b/ts/components/conversation/conversation-details/ConversationDetailsActions.tsx
index 707682a2cf..d60a67c2a9 100644
--- a/ts/components/conversation/conversation-details/ConversationDetailsActions.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetailsActions.tsx
@@ -1,16 +1,19 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
+import classNames from 'classnames';
 
 import { LocalizerType } from '../../../types/Util';
 import { ConfirmationModal } from '../../ConfirmationModal';
+import { Tooltip, TooltipPlacement } from '../../Tooltip';
 
 import { PanelRow } from './PanelRow';
 import { PanelSection } from './PanelSection';
 import { ConversationDetailsIcon } from './ConversationDetailsIcon';
 
 export type Props = {
+  cannotLeaveBecauseYouAreLastAdmin: boolean;
   conversationTitle: string;
   onBlockAndDelete: () => void;
   onDelete: () => void;
@@ -18,6 +21,7 @@ export type Props = {
 };
 
 export const ConversationDetailsActions: React.ComponentType<Props> = ({
+  cannotLeaveBecauseYouAreLastAdmin,
   conversationTitle,
   onBlockAndDelete,
   onDelete,
@@ -26,23 +30,47 @@ export const ConversationDetailsActions: React.ComponentType<Props> = ({
   const [confirmingLeave, setConfirmingLeave] = React.useState<boolean>(false);
   const [confirmingBlock, setConfirmingBlock] = React.useState<boolean>(false);
 
+  let leaveGroupNode = (
+    <PanelRow
+      disabled={cannotLeaveBecauseYouAreLastAdmin}
+      onClick={() => setConfirmingLeave(true)}
+      icon={
+        <ConversationDetailsIcon
+          ariaLabel={i18n('ConversationDetailsActions--leave-group')}
+          disabled={cannotLeaveBecauseYouAreLastAdmin}
+          icon="leave"
+        />
+      }
+      label={
+        <div
+          className={classNames(
+            'module-conversation-details__leave-group',
+            cannotLeaveBecauseYouAreLastAdmin &&
+              'module-conversation-details__leave-group--disabled'
+          )}
+        >
+          {i18n('ConversationDetailsActions--leave-group')}
+        </div>
+      }
+    />
+  );
+  if (cannotLeaveBecauseYouAreLastAdmin) {
+    leaveGroupNode = (
+      <Tooltip
+        content={i18n(
+          'ConversationDetailsActions--leave-group-must-choose-new-admin'
+        )}
+        direction={TooltipPlacement.Top}
+      >
+        {leaveGroupNode}
+      </Tooltip>
+    );
+  }
+
   return (
     <>
       <PanelSection>
-        <PanelRow
-          onClick={() => setConfirmingLeave(true)}
-          icon={
-            <ConversationDetailsIcon
-              ariaLabel={i18n('ConversationDetailsActions--leave-group')}
-              icon="leave"
-            />
-          }
-          label={
-            <div className="module-conversation-details__leave-group">
-              {i18n('ConversationDetailsActions--leave-group')}
-            </div>
-          }
-        />
+        {leaveGroupNode}
         <PanelRow
           onClick={() => setConfirmingBlock(true)}
           icon={
diff --git a/ts/components/conversation/conversation-details/ConversationDetailsIcon.tsx b/ts/components/conversation/conversation-details/ConversationDetailsIcon.tsx
index 4f47818a1a..9feef009a7 100644
--- a/ts/components/conversation/conversation-details/ConversationDetailsIcon.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetailsIcon.tsx
@@ -1,12 +1,14 @@
-// Copyright 2020 Signal Messenger, LLC
+// Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
+import classNames from 'classnames';
 
 import { bemGenerator } from './util';
 
 export type Props = {
   ariaLabel: string;
+  disabled?: boolean;
   icon: string;
   onClick?: () => void;
 };
@@ -15,16 +17,26 @@ const bem = bemGenerator('module-conversation-details-icon');
 
 export const ConversationDetailsIcon: React.ComponentType<Props> = ({
   ariaLabel,
+  disabled,
   icon,
   onClick,
 }) => {
-  const content = <div className={bem('icon', icon)} />;
+  const iconClassName = bem('icon', icon);
+  const content = (
+    <div
+      className={classNames(
+        iconClassName,
+        disabled && `${iconClassName}--disabled`
+      )}
+    />
+  );
 
   if (onClick) {
     return (
       <button
         aria-label={ariaLabel}
         className={bem('button')}
+        disabled={disabled}
         type="button"
         onClick={onClick}
       >
diff --git a/ts/components/conversation/conversation-details/PanelRow.tsx b/ts/components/conversation/conversation-details/PanelRow.tsx
index 06550b923b..6bde283efd 100644
--- a/ts/components/conversation/conversation-details/PanelRow.tsx
+++ b/ts/components/conversation/conversation-details/PanelRow.tsx
@@ -8,6 +8,7 @@ import { bemGenerator } from './util';
 export type Props = {
   alwaysShowActions?: boolean;
   className?: string;
+  disabled?: boolean;
   icon?: React.ReactNode;
   label: string | React.ReactNode;
   info?: string;
@@ -21,6 +22,7 @@ const bem = bemGenerator('module-conversation-details-panel-row');
 export const PanelRow: React.ComponentType<Props> = ({
   alwaysShowActions,
   className,
+  disabled,
   icon,
   label,
   info,
@@ -45,6 +47,7 @@ export const PanelRow: React.ComponentType<Props> = ({
   if (onClick) {
     return (
       <button
+        disabled={disabled}
         type="button"
         className={classNames(bem('root', 'button'), className)}
         onClick={onClick}