diff --git a/web/chat/chat-input-text-area.react.js b/web/chat/chat-input-text-area.react.js
--- a/web/chat/chat-input-text-area.react.js
+++ b/web/chat/chat-input-text-area.react.js
@@ -11,6 +11,7 @@
   +focus: boolean,
   +currentText: string,
   +setCurrentText: (text: string) => void,
+  +onChangePosition: any => void,
 };
 type Props = {
   ...BaseProps,
@@ -39,6 +40,7 @@
       const newHeight = Math.min(textarea.scrollHeight, 150);
       textarea.style.height = `${newHeight}px`;
     }
+    this.props.onChangePosition();
   }
 
   render() {
diff --git a/web/chat/edit-message-provider.js b/web/chat/edit-message-provider.js
--- a/web/chat/edit-message-provider.js
+++ b/web/chat/edit-message-provider.js
@@ -7,11 +7,19 @@
 import type { ChatMessageInfoItem } from 'lib/selectors/chat-selectors.js';
 import type { ThreadInfo } from 'lib/types/thread-types';
 
+export type ModalPosition = {
+  +left: number,
+  +top: number,
+  +width: number,
+  +height: number,
+};
+
 export type EditState = {
   +messageInfo: ChatMessageInfoItem,
   +threadInfo: ThreadInfo,
   +editedMessageDraft: ?string,
   +isError: boolean,
+  +position?: ModalPosition,
 };
 
 type EditModalContextType = {
@@ -20,6 +28,7 @@
   +editState: ?EditState,
   +setDraft: string => void,
   +setError: boolean => void,
+  +updatePosition: ModalPosition => void,
 };
 
 const EditModalContext: React.Context<EditModalContextType> =
@@ -29,6 +38,7 @@
     editState: null,
     setDraft: () => {},
     setError: () => {},
+    updatePosition: () => {},
   });
 
 type Props = {
@@ -77,6 +87,20 @@
     },
     [editState, setEditState],
   );
+
+  const updatePosition = React.useCallback(
+    (position: ModalPosition) => {
+      if (!editState) {
+        return;
+      }
+      setEditState({
+        ...editState,
+        position,
+      });
+    },
+    [editState, setEditState],
+  );
+
   const value = React.useMemo(
     () => ({
       renderEditModal,
@@ -84,8 +108,16 @@
       editState,
       setDraft,
       setError,
+      updatePosition,
     }),
-    [renderEditModal, clearEditModal, editState, setDraft, setError],
+    [
+      renderEditModal,
+      clearEditModal,
+      editState,
+      setDraft,
+      setError,
+      updatePosition,
+    ],
   );
 
   let modalOverlay;
diff --git a/web/chat/edit-text-message.react.js b/web/chat/edit-text-message.react.js
--- a/web/chat/edit-text-message.react.js
+++ b/web/chat/edit-text-message.react.js
@@ -15,7 +15,7 @@
 import ChatInputTextArea from './chat-input-text-area.react.js';
 import ComposedMessage from './composed-message.react.js';
 import { useEditModalContext } from './edit-message-provider.js';
-import type { EditState } from './edit-message-provider.js';
+import type { EditState, ModalPosition } from './edit-message-provider.js';
 import css from './edit-text-message.css';
 
 type BaseProps = {
@@ -35,6 +35,7 @@
   ) => Promise<SendEditMessageResult>,
   +setError: boolean => void,
   +setDraft: string => void,
+  +updatePosition: ModalPosition => void,
 };
 class EditTextMessage extends React.PureComponent<Props> {
   myRef: { current: null | HTMLDivElement };
@@ -42,8 +43,35 @@
   constructor(props: any) {
     super(props);
     this.myRef = React.createRef();
+
+    this.updateDimensions = this.updateDimensions.bind(this);
+  }
+
+  componentDidMount() {
+    this.updateDimensions();
+    window.addEventListener('resize', this.updateDimensions, false);
+  }
+
+  componentWillUnmount() {
+    window.removeEventListener('resize', this.updateDimensions, false);
   }
 
+  updateDimensions = () => {
+    if (!this.props.background) {
+      return;
+    }
+    if (this.myRef.current) {
+      const { left, top, width, height } =
+        this.myRef.current.getBoundingClientRect();
+      this.props.updatePosition({
+        left,
+        top,
+        width,
+        height,
+      });
+    }
+  };
+
   render() {
     invariant(
       this.props.item.messageInfo.type === messageTypes.TEXT,
@@ -82,6 +110,7 @@
             focus={!this.props.background}
             currentText={editedMessageDraft}
             setCurrentText={this.props.setDraft}
+            onChangePosition={this.updateDimensions}
           />
         </div>
         <div className={css.bottomRow}>
@@ -141,7 +170,7 @@
 
 const ConnectedEditTextMessage: React.ComponentType<BaseProps> =
   React.memo<BaseProps>(function ConnectedEditTextMessage(props) {
-    const { editState, clearEditModal, setError, setDraft } =
+    const { editState, clearEditModal, setError, setDraft, updatePosition } =
       useEditModalContext();
     const editMessage = useEditMessage();
     return (
@@ -152,6 +181,7 @@
         editMessage={editMessage}
         setError={setError}
         setDraft={setDraft}
+        updatePosition={updatePosition}
       />
     );
   });