diff --git a/app/main/forms.py b/app/main/forms.py
index 8a4f09e2c..77c6d7cfd 100644
--- a/app/main/forms.py
+++ b/app/main/forms.py
@@ -2161,3 +2161,23 @@ class BroadcastAreaForm(StripWhitespaceForm):
         return cls(choices=[
             (area.id, area.name) for area in sorted(library)
         ])
+
+
+class BroadcastAreaFormWithSelectAll(BroadcastAreaForm):
+
+    select_all = govukCheckboxField('Select all')
+
+    @classmethod
+    def from_library(cls, library, select_all_choice):
+        instance = super().from_library(library)
+        (
+            instance.select_all.area_slug,
+            instance.select_all.label.text,
+        ) = select_all_choice
+        return instance
+
+    @property
+    def selected_areas(self):
+        if self.select_all.data:
+            return [self.select_all.area_slug]
+        return self.areas.data
diff --git a/app/main/views/broadcast.py b/app/main/views/broadcast.py
index ff35b505d..180536ba8 100644
--- a/app/main/views/broadcast.py
+++ b/app/main/views/broadcast.py
@@ -12,6 +12,7 @@ from app import current_service
 from app.main import main
 from app.main.forms import (
     BroadcastAreaForm,
+    BroadcastAreaFormWithSelectAll,
     ChooseBroadcastDurationForm,
     SearchByNameForm,
 )
@@ -118,6 +119,16 @@ def choose_broadcast_area(service_id, broadcast_message_id, library_slug):
         service_id=current_service.id,
     )
     library = BroadcastMessage.libraries.get(library_slug)
+
+    if library.is_group:
+        return render_template(
+            'views/broadcast/areas-with-sub-areas.html',
+            search_form=SearchByNameForm(),
+            show_search_form=(len(library) > 7),
+            library=library,
+            broadcast_message=broadcast_message,
+        )
+
     form = BroadcastAreaForm.from_library(library)
     if form.validate_on_submit():
         broadcast_message.add_areas(*form.areas.data)
@@ -136,6 +147,41 @@ def choose_broadcast_area(service_id, broadcast_message_id, library_slug):
     )
 
 
+@main.route(
+    '/services/<uuid:service_id>/broadcast/<uuid:broadcast_message_id>/libraries/<library_slug>/<area_slug>',
+    methods=['GET', 'POST'],
+)
+@user_has_permissions('send_messages')
+@service_has_permission('broadcast')
+def choose_broadcast_sub_area(service_id, broadcast_message_id, library_slug, area_slug):
+    broadcast_message = BroadcastMessage.from_id(
+        broadcast_message_id,
+        service_id=current_service.id,
+    )
+    area = BroadcastMessage.libraries.get_areas(area_slug)[0]
+
+    form = BroadcastAreaFormWithSelectAll.from_library(
+        area.sub_areas,
+        select_all_choice=(area.id, f'All of {area.name}'),
+    )
+    if form.validate_on_submit():
+        broadcast_message.add_areas(*form.selected_areas)
+        return redirect(url_for(
+            '.preview_broadcast_areas',
+            service_id=current_service.id,
+            broadcast_message_id=broadcast_message.id,
+        ))
+    return render_template(
+        'views/broadcast/sub-areas.html',
+        form=form,
+        search_form=SearchByNameForm(),
+        show_search_form=(len(form.areas.choices) > 7),
+        library_slug=library_slug,
+        page_title=f'Choose an area of {area.name}',
+        broadcast_message=broadcast_message,
+    )
+
+
 @main.route('/services/<uuid:service_id>/broadcast/<uuid:broadcast_message_id>/remove/<area_slug>')
 @user_has_permissions('send_messages')
 @service_has_permission('broadcast')
diff --git a/app/navigation.py b/app/navigation.py
index f5ddc5323..204c50f0b 100644
--- a/app/navigation.py
+++ b/app/navigation.py
@@ -359,6 +359,7 @@ class HeaderNavigation(Navigation):
         'preview_broadcast_areas',
         'choose_broadcast_library',
         'choose_broadcast_area',
+        'choose_broadcast_sub_area',
         'remove_broadcast_area',
         'preview_broadcast_message',
         'view_broadcast_message',
@@ -420,6 +421,7 @@ class MainNavigation(Navigation):
             'preview_broadcast_areas',
             'choose_broadcast_library',
             'choose_broadcast_area',
+            'choose_broadcast_sub_area',
             'remove_broadcast_area',
             'preview_broadcast_message',
             'view_broadcast_message',
@@ -1016,6 +1018,7 @@ class CaseworkNavigation(Navigation):
         'preview_broadcast_areas',
         'choose_broadcast_library',
         'choose_broadcast_area',
+        'choose_broadcast_sub_area',
         'remove_broadcast_area',
         'preview_broadcast_message',
         'view_broadcast_message',
@@ -1340,6 +1343,7 @@ class OrgNavigation(Navigation):
         'preview_broadcast_areas',
         'choose_broadcast_library',
         'choose_broadcast_area',
+        'choose_broadcast_sub_area',
         'remove_broadcast_area',
         'preview_broadcast_message',
         'view_broadcast_message',
diff --git a/app/templates/views/broadcast/areas-with-sub-areas.html b/app/templates/views/broadcast/areas-with-sub-areas.html
new file mode 100644
index 000000000..c62e09ab4
--- /dev/null
+++ b/app/templates/views/broadcast/areas-with-sub-areas.html
@@ -0,0 +1,25 @@
+{% from "components/page-header.html" import page_header %}
+{% from "components/live-search.html" import live_search %}
+
+{% extends "withnav_template.html" %}
+
+{% block service_page_title %}
+  {{ library.name }}
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  {{ page_header(
+    library.name,
+    back_link=url_for('.choose_broadcast_library', service_id=current_service.id, broadcast_message_id=broadcast_message.id),
+  )}}
+
+  {{ live_search(target_selector='.file-list-item', show=show_search_form, form=search_form, label='Search by name') }}
+
+  {% for area in library|sort %}
+    <div class="file-list-item">
+      <a class="file-list-filename-large govuk-link govuk-link--no-visited-state" href="{{ url_for('.choose_broadcast_sub_area', service_id=current_service.id, broadcast_message_id=broadcast_message.id, library_slug=library.id, area_slug=area.id) }}">{{ area.name }}</a>
+    </div>
+  {% endfor %}
+
+{% endblock %}
diff --git a/app/templates/views/broadcast/sub-areas.html b/app/templates/views/broadcast/sub-areas.html
new file mode 100644
index 000000000..6a9f6dfd9
--- /dev/null
+++ b/app/templates/views/broadcast/sub-areas.html
@@ -0,0 +1,33 @@
+{% from "components/page-header.html" import page_header %}
+{% from "components/page-footer.html" import sticky_page_footer %}
+{% from "components/form.html" import form_wrapper %}
+{% from "components/live-search.html" import live_search %}
+
+{% extends "withnav_template.html" %}
+
+{% block service_page_title %}
+  {{ page_title }}
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  {{ page_header(
+    page_title,
+    back_link=url_for('.choose_broadcast_library', service_id=current_service.id, broadcast_message_id=broadcast_message.id),
+  )}}
+
+  {% call form_wrapper() %}
+
+    <div class="form-group govuk-!-margin-bottom-4">
+      {{ form.select_all }}
+    </div>
+
+    {{ live_search(target_selector='.multiple-choice', show=show_search_form, form=search_form, label='Or by electoral ward') }}
+
+    {{ form.areas }}
+
+    {{ sticky_page_footer('Add to broadcast') }}
+
+  {% endcall %}
+
+{% endblock %}
diff --git a/tests/app/main/views/test_broadcast.py b/tests/app/main/views/test_broadcast.py
index 0570e1963..a223b6982 100644
--- a/tests/app/main/views/test_broadcast.py
+++ b/tests/app/main/views/test_broadcast.py
@@ -1,5 +1,6 @@
 import json
 import uuid
+from functools import partial
 
 import pytest
 from flask import url_for
@@ -257,12 +258,104 @@ def test_choose_broadcast_area_page(
     fake_uuid,
 ):
     service_one['permissions'] += ['broadcast']
-    client_request.get(
+    page = client_request.get(
         '.choose_broadcast_area',
         service_id=SERVICE_ONE_ID,
         broadcast_message_id=fake_uuid,
         library_slug='countries',
     )
+    assert [
+        (
+            choice.select_one('input')['value'],
+            normalize_spaces(choice.select_one('label').text),
+        )
+        for choice in page.select('form[method=post] .govuk-checkboxes__item')
+    ] == [
+        ('countries-E92000001', 'England'),
+        ('countries-N92000002', 'Northern Ireland'),
+        ('countries-S92000003', 'Scotland'),
+        ('countries-W92000004', 'Wales'),
+    ]
+
+
+def test_choose_broadcast_area_page_for_area_with_sub_areas(
+    client_request,
+    service_one,
+    mock_get_draft_broadcast_message,
+    fake_uuid,
+):
+    service_one['permissions'] += ['broadcast']
+    page = client_request.get(
+        '.choose_broadcast_area',
+        service_id=SERVICE_ONE_ID,
+        broadcast_message_id=fake_uuid,
+        library_slug='electoral-wards-of-the-united-kingdom',
+    )
+    partial_url_for = partial(
+        url_for,
+        'main.choose_broadcast_sub_area',
+        service_id=SERVICE_ONE_ID,
+        broadcast_message_id=fake_uuid,
+        library_slug='electoral-wards-of-the-united-kingdom',
+    )
+    choices = [
+        (
+            choice.select_one('a.file-list-filename-large')['href'],
+            normalize_spaces(choice.text),
+        )
+        for choice in page.select('.file-list-item')
+    ]
+    assert len(choices) == 379
+    assert choices[:2] == [
+        (
+            partial_url_for(area_slug='electoral-wards-of-the-united-kingdom-S12000033'),
+            'Aberdeen City',
+        ),
+        (
+            partial_url_for(area_slug='electoral-wards-of-the-united-kingdom-S12000034'),
+            'Aberdeenshire',
+        ),
+    ]
+    assert choices[-1:] == [
+        (
+            partial_url_for(area_slug='electoral-wards-of-the-united-kingdom-E06000014'),
+            'York',
+        ),
+    ]
+
+
+def test_choose_broadcast_sub_area_page(
+    client_request,
+    service_one,
+    mock_get_draft_broadcast_message,
+    fake_uuid,
+):
+    service_one['permissions'] += ['broadcast']
+    page = client_request.get(
+        'main.choose_broadcast_sub_area',
+        service_id=SERVICE_ONE_ID,
+        broadcast_message_id=fake_uuid,
+        library_slug='electoral-wards-of-the-united-kingdom',
+        area_slug='electoral-wards-of-the-united-kingdom-S12000033',
+    )
+    assert normalize_spaces(page.select_one('h1').text) == (
+        'Choose an area of Aberdeen City'
+    )
+    choices = [
+        (
+            choice.select_one('input')['value'],
+            normalize_spaces(choice.select_one('label').text),
+        )
+        for choice in page.select('form[method=post] .govuk-checkboxes__item')
+    ]
+    assert choices[:3] == [
+        ('y', 'All of Aberdeen City'),
+        ('electoral-wards-of-the-united-kingdom-S13002845', 'Airyhall/Broomhill/Garthdee'),
+        ('electoral-wards-of-the-united-kingdom-S13002836', 'Bridge of Don'),
+    ]
+    assert choices[-1:] == [
+        ('electoral-wards-of-the-united-kingdom-S13002846', 'Torry/Ferryhill'),
+    ]
 
 
 def test_add_broadcast_area(
@@ -291,6 +384,57 @@ def test_add_broadcast_area(
     )
 
 
+@pytest.mark.parametrize('post_data, expected_selected', (
+    ({
+        'select_all': 'y',
+        'areas': [
+            'electoral-wards-of-the-united-kingdom-S13002845',
+        ]
+    }, [
+        'electoral-wards-of-the-united-kingdom-S12000033',
+        # S13002845 is ignored because the user chose ‘Select all…’
+    ]),
+    ({
+        'areas': [
+            'electoral-wards-of-the-united-kingdom-S13002845',
+            'electoral-wards-of-the-united-kingdom-S13002836',
+        ]
+    }, [
+        'electoral-wards-of-the-united-kingdom-S13002845',
+        'electoral-wards-of-the-united-kingdom-S13002836',
+    ]),
+))
+def test_add_broadcast_sub_area(
+    client_request,
+    service_one,
+    mock_get_draft_broadcast_message,
+    mock_update_broadcast_message,
+    fake_uuid,
+    post_data,
+    expected_selected,
+):
+    service_one['permissions'] += ['broadcast']
+    client_request.post(
+        '.choose_broadcast_sub_area',
+        service_id=SERVICE_ONE_ID,
+        broadcast_message_id=fake_uuid,
+        library_slug='countries',
+        area_slug='electoral-wards-of-the-united-kingdom-S12000033',
+        _data=post_data,
+    )
+    mock_update_broadcast_message.assert_called_once_with(
+        service_id=SERVICE_ONE_ID,
+        broadcast_message_id=fake_uuid,
+        data={
+            'areas': [
+                # These two areas are on the broadcast already
+                'countries-E92000001',
+                'countries-S92000003',
+            ] + expected_selected
+        },
+    )
+
+
 def test_remove_broadcast_area_page(
     client_request,
     service_one,