diff --git a/h/static/scripts/group-forms/components/EditGroupMembersForm.tsx b/h/static/scripts/group-forms/components/EditGroupMembersForm.tsx
index 77365eab095..dc18f171b96 100644
--- a/h/static/scripts/group-forms/components/EditGroupMembersForm.tsx
+++ b/h/static/scripts/group-forms/components/EditGroupMembersForm.tsx
@@ -1,5 +1,5 @@
-import { DataTable, Scroll } from '@hypothesis/frontend-shared';
-import { useEffect, useState } from 'preact/hooks';
+import { DataTable, Input, Scroll } from '@hypothesis/frontend-shared';
+import { useEffect, useMemo, useState } from 'preact/hooks';
 
 import { routes } from '../routes';
 import type { Group } from '../config';
@@ -56,6 +56,8 @@ export default function EditGroupMembersForm({
     },
   ];
 
+  const [filter, setFilter] = useState('');
+
   const renderRow = (user: MemberRow, field: keyof MemberRow) => {
     switch (field) {
       case 'username':
@@ -76,11 +78,46 @@ export default function EditGroupMembersForm({
 
   const memberText = pluralize(members?.length ?? 0, 'member', 'members');
 
+  const filteredMembers = useMemo(() => {
+    if (!filter || !members) {
+      return members;
+    }
+
+    const normalizedFilter = filter.toLowerCase();
+
+    // nb. We can get away with lower-casing name and filter to do
+    // case-insensitive search because of the character set restrictions on
+    // usernames. This would be incorrect for Unicode text.
+    return members.filter(m =>
+      m.username.toLowerCase().includes(normalizedFilter),
+    );
+  }, [filter, members]);
+
+  let emptyMessage;
+  if (members !== null && members.length > 0 && filter) {
+    emptyMessage = (
+      <div data-testid="no-filter-match">
+        No members match the filter {'"'}
+        <b>{filter}</b>
+        {'"'}
+      </div>
+    );
+  }
+
   return (
     <FormContainer title="Edit group members">
       <GroupFormHeader group={group} />
       <hr />
-      <div className="flex py-3">
+      <div className="flex py-3 items-center">
+        {/* Input has `w-full` style. Wrap in container to stop it stretching to full width of row. */}
+        <div>
+          <Input
+            aria-label="Search members"
+            data-testid="search-input"
+            placeholder="Search…"
+            onInput={e => setFilter((e.target as HTMLInputElement).value)}
+          />
+        </div>
         <div className="grow" />
         <div data-testid="member-count">
           {members?.length ?? '...'} {memberText}
@@ -91,9 +128,10 @@ export default function EditGroupMembersForm({
         <Scroll>
           <DataTable
             title="Group members"
-            rows={members ?? []}
+            rows={filteredMembers ?? []}
             columns={columns}
             renderItem={renderRow}
+            emptyMessage={emptyMessage}
           />
         </Scroll>
       </div>
diff --git a/h/static/scripts/group-forms/components/test/EditGroupMembersForm-test.js b/h/static/scripts/group-forms/components/test/EditGroupMembersForm-test.js
index d95725ad576..66bc420559a 100644
--- a/h/static/scripts/group-forms/components/test/EditGroupMembersForm-test.js
+++ b/h/static/scripts/group-forms/components/test/EditGroupMembersForm-test.js
@@ -26,6 +26,9 @@ describe('EditGroupMembersForm', () => {
       {
         username: 'bob',
       },
+      {
+        username: 'johnsmith',
+      },
     ]);
 
     $imports.$mock({
@@ -52,24 +55,37 @@ describe('EditGroupMembersForm', () => {
       return wrapper.find('ErrorNotice').prop('message') !== null;
     });
 
+  const getRenderedUsers = wrapper => {
+    return wrapper.find('[data-testid="username"]').map(node => node.text());
+  };
+
+  const enterFilterValue = (wrapper, value) => {
+    const filter = wrapper.find('input[data-testid="search-input"]');
+    filter.getDOMNode().value = value;
+    filter.simulate('input');
+  };
+
   it('fetches and displays members', async () => {
     const wrapper = createForm();
     assert.calledWith(fakeCallAPI, '/api/groups/1234/members');
 
     await waitForTable(wrapper);
 
-    const users = wrapper.find('[data-testid="username"]');
-    assert.equal(users.length, 1);
-    assert.equal(users.at(0).text(), 'bob');
+    const users = getRenderedUsers(wrapper);
+    assert.deepEqual(users, ['bob', 'johnsmith']);
   });
 
   it('displays member count', async () => {
+    fakeCallAPI.withArgs('/api/groups/1234/members').resolves([
+      {
+        username: 'bob',
+      },
+    ]);
     const wrapper = createForm();
     const memberCount = wrapper.find('[data-testid="member-count"]');
     assert.equal(memberCount.text(), '... members');
 
     await waitForTable(wrapper);
-
     assert.equal(memberCount.text(), '1 member');
   });
 
@@ -94,4 +110,31 @@ describe('EditGroupMembersForm', () => {
     // Unmount while fetching. This should abort the request.
     wrapper.unmount();
   });
+
+  it('filters members', async () => {
+    const wrapper = createForm();
+    await waitForTable(wrapper);
+
+    // Filter should remove non-matching users
+    enterFilterValue(wrapper, 'john');
+    const users = getRenderedUsers(wrapper);
+    assert.deepEqual(users, ['johnsmith']);
+
+    // Filter should match anywhere in username
+    enterFilterValue(wrapper, 'smith');
+    const users2 = getRenderedUsers(wrapper);
+    assert.deepEqual(users2, ['johnsmith']);
+
+    // Filter should be case-insensitive
+    enterFilterValue(wrapper, 'BOB');
+    const users3 = getRenderedUsers(wrapper);
+    assert.deepEqual(users3, ['bob']);
+  });
+
+  it('displays message if filter does not match any members', async () => {
+    const wrapper = createForm();
+    await waitForTable(wrapper);
+    enterFilterValue(wrapper, 'no-match');
+    assert.isTrue(wrapper.exists('[data-testid="no-filter-match"]'));
+  });
 });