diff --git a/src/unread/__tests__/unreadHuddlesReducer-test.js b/src/unread/__tests__/unreadHuddlesReducer-test.js
index 6d2fa1042fd..0f9a28e6172 100644
--- a/src/unread/__tests__/unreadHuddlesReducer-test.js
+++ b/src/unread/__tests__/unreadHuddlesReducer-test.js
@@ -118,7 +118,7 @@ describe('unreadHuddlesReducer', () => {
       expect(actualState).toBe(initialState);
     });
 
-    test('if message is sent by self, do not mutate state', () => {
+    test('if message has "read" flag, do not mutate state', () => {
       const selfUser = { ...eg.selfUser, user_id: makeUserId(1) };
       const user2 = { ...eg.otherUser, user_id: makeUserId(2) };
       const user3 = { ...eg.thirdUser, user_id: makeUserId(3) };
@@ -126,8 +126,9 @@ describe('unreadHuddlesReducer', () => {
       const initialState = deepFreeze([]);
 
       const message2 = eg.pmMessage({
-        sender: selfUser,
+        sender: user2,
         recipients: [selfUser, user2, user3],
+        flags: ['read'],
       });
 
       const action = deepFreeze({
diff --git a/src/unread/__tests__/unreadMentionsReducer-test.js b/src/unread/__tests__/unreadMentionsReducer-test.js
index 239ea6d7cef..7ce7311591a 100644
--- a/src/unread/__tests__/unreadMentionsReducer-test.js
+++ b/src/unread/__tests__/unreadMentionsReducer-test.js
@@ -67,6 +67,22 @@ describe('unreadMentionsReducer', () => {
       expect(actualState).toBe(initialState);
     });
 
+    test('if message has "read" flag, do not mutate state', () => {
+      const initialState = deepFreeze([]);
+
+      const action = deepFreeze({
+        type: EVENT_NEW_MESSAGE,
+        message: {
+          id: 2,
+          flags: ['mentioned', 'read'],
+        },
+      });
+
+      const actualState = unreadMentionsReducer(initialState, action);
+
+      expect(actualState).toBe(initialState);
+    });
+
     test('if message id already exists, do not mutate state', () => {
       const initialState = deepFreeze([1, 2]);
 
diff --git a/src/unread/__tests__/unreadModel-test.js b/src/unread/__tests__/unreadModel-test.js
index 0cc91bad201..9aa3227ba4b 100644
--- a/src/unread/__tests__/unreadModel-test.js
+++ b/src/unread/__tests__/unreadModel-test.js
@@ -84,10 +84,10 @@ describe('stream substate', () => {
       expect(state.streams).toBe(baseState.streams);
     });
 
-    test('if message is sent by self, do not mutate state', () => {
+    test('if message has "read" flag, do not mutate state', () => {
       const state = reducer(
         baseState,
-        action(eg.streamMessage({ sender: eg.selfUser })),
+        action(eg.streamMessage({ sender: eg.selfUser, flags: ['read'] })),
         eg.plusReduxState,
       );
       expect(state).toBe(baseState);
diff --git a/src/unread/__tests__/unreadPmsReducer-test.js b/src/unread/__tests__/unreadPmsReducer-test.js
index a571c0c27c6..16f14edfc27 100644
--- a/src/unread/__tests__/unreadPmsReducer-test.js
+++ b/src/unread/__tests__/unreadPmsReducer-test.js
@@ -111,11 +111,12 @@ describe('unreadPmsReducer', () => {
       expect(actualState).toBe(initialState);
     });
 
-    test('if message is sent by self, do not mutate state', () => {
+    test('if message is marked read, do not mutate state', () => {
       const initialState = deepFreeze([]);
       const message1 = eg.pmMessage({
-        sender: eg.selfUser,
+        sender: eg.otherUser,
         recipients: [eg.otherUser, eg.selfUser],
+        flags: ['read'],
       });
 
       const action = deepFreeze({
diff --git a/src/unread/unreadHuddlesReducer.js b/src/unread/unreadHuddlesReducer.js
index efa06de2820..c0f3799c00b 100644
--- a/src/unread/unreadHuddlesReducer.js
+++ b/src/unread/unreadHuddlesReducer.js
@@ -24,7 +24,14 @@ const eventNewMessage = (state, action) => {
     return state;
   }
 
-  if (action.ownUserId === action.message.sender_id) {
+  // TODO: In reality, we should error if `flags` is undefined, since it's
+  // always supposed to be set. However, our tests currently don't pass flags
+  // into these events, making it annoying to fix this. We should fix the
+  // tests, then change this to error if `flags` is undefined. See [1] for
+  // details.
+  //
+  // [1]: https://github.com/zulip/zulip-mobile/pull/4710/files#r627850775
+  if (action.message.flags?.includes('read')) {
     return state;
   }
 
diff --git a/src/unread/unreadMentionsReducer.js b/src/unread/unreadMentionsReducer.js
index 60024d1b027..37bdf29cdcd 100644
--- a/src/unread/unreadMentionsReducer.js
+++ b/src/unread/unreadMentionsReducer.js
@@ -46,6 +46,9 @@ export default (state: UnreadMentionsState = initialState, action: Action): Unre
       if (!flags) {
         throw new Error('action.message.flags should be defined.');
       }
+      if (flags.includes('read')) {
+        return state;
+      }
       return (flags.includes('mentioned') || flags.includes('wildcard_mentioned'))
         && !state.includes(action.message.id)
         ? addItemsToArray(state, [action.message.id])
diff --git a/src/unread/unreadModel.js b/src/unread/unreadModel.js
index f8c4deac1e0..59ac8be670b 100644
--- a/src/unread/unreadModel.js
+++ b/src/unread/unreadModel.js
@@ -22,7 +22,6 @@ import {
   MESSAGE_FETCH_COMPLETE,
   REALM_INIT,
 } from '../actionConstants';
-import { getOwnUserId } from '../users/userSelectors';
 
 //
 //
@@ -146,7 +145,14 @@ function streamsReducer(
         return state;
       }
 
-      if (message.sender_id === getOwnUserId(globalState)) {
+      // TODO: In reality, we should error if `flags` is undefined, since it's
+      // always supposed to be set. However, our tests currently don't pass flags
+      // into these events, making it annoying to fix this. We should fix the
+      // tests, then change this to error if `flags` is undefined. See [1] for
+      // details.
+      //
+      // [1]: https://github.com/zulip/zulip-mobile/pull/4710/files#r627850775
+      if (message.flags?.includes('read')) {
         return state;
       }
 
diff --git a/src/unread/unreadPmsReducer.js b/src/unread/unreadPmsReducer.js
index 6562789fc7a..2d4567a61d5 100644
--- a/src/unread/unreadPmsReducer.js
+++ b/src/unread/unreadPmsReducer.js
@@ -24,7 +24,14 @@ const eventNewMessage = (state, action) => {
     return state;
   }
 
-  if (action.ownUserId === action.message.sender_id) {
+  // TODO: In reality, we should error if `flags` is undefined, since it's
+  // always supposed to be set. However, our tests currently don't pass flags
+  // into these events, making it annoying to fix this. We should fix the
+  // tests, then change this to error if `flags` is undefined. See [1] for
+  // details.
+  //
+  // [1]: https://github.com/zulip/zulip-mobile/pull/4710/files#r627850775
+  if (action.message.flags?.includes('read')) {
     return state;
   }