diff --git a/defaults/main.yml b/defaults/main.yml
index eaafea5a..cf576e6d 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -162,6 +162,7 @@ horizon_endpoint_type: internalURL
 
 horizon_server_name: "{{ ansible_facts['fqdn'] | default('horizon') }}"
 
+horizon_apache_mpm_backend: "{{ openstack_apache_mpm_backend | default('event') }}"
 horizon_apache_servertokens: "Prod"
 horizon_apache_serversignature: "Off"
 horizon_log_level: info
diff --git a/releasenotes/notes/horizon_apache_mpm-2a34436635f1bef9.yaml b/releasenotes/notes/horizon_apache_mpm-2a34436635f1bef9.yaml
new file mode 100644
index 00000000..63158ddc
--- /dev/null
+++ b/releasenotes/notes/horizon_apache_mpm-2a34436635f1bef9.yaml
@@ -0,0 +1,8 @@
+---
+
+upgrade:
+  - |
+    In order to align used Apache MPM across the board, Horizon default
+    MPM is switched from ``worker`` to ``event``.
+    A variable ``horizon_apache_mpm_backend`` was introduced to define
+    the MPM in use.
diff --git a/tasks/horizon_apache.yml b/tasks/horizon_apache.yml
index 018f7ff0..cf9afd8a 100644
--- a/tasks/horizon_apache.yml
+++ b/tasks/horizon_apache.yml
@@ -13,6 +13,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Ensure apache2 MPM for Debian/Ubuntu
+  apache2_module:
+    name: "{{ item.name }}"
+    state: "{{ item.state }}"
+    ignore_configcheck: yes
+    warn_mpm_absent: false
+  with_items: "{{ horizon_apache_mpms | sort(attribute='state') }}"
+  when:
+    - ansible_facts['pkg_mgr'] == 'apt'
+  notify: Restart wsgi process
+
+- name: Ensure apache2 MPM for EL
+  copy:
+    content: |
+      LoadModule mpm_{{ horizon_apache_mpm_backend }}_module modules/mod_mpm_{{ horizon_apache_mpm_backend }}.so
+
+    dest: /etc/httpd/conf.modules.d/00-mpm.conf
+    mode: "0644"
+  when:
+    - ansible_facts['pkg_mgr'] == 'dnf'
+  notify: Restart wsgi process
+
 # NOTE(hwoarang): Module enable/disable process is only functional on Debian
 - name: Enable apache2 modules
   apache2_module:
diff --git a/vars/debian.yml b/vars/debian.yml
index eda4fa34..fbea8c0a 100644
--- a/vars/debian.yml
+++ b/vars/debian.yml
@@ -53,15 +53,19 @@ horizon_apache_default_sites:
   - "/etc/apache2/sites-enabled/000-default.conf"
   - "/etc/apache2/conf-enabled/other-vhosts-access-log.conf"
 
+horizon_apache_mpms:
+  - name: "mpm_event"
+    state: "{{ (horizon_apache_mpm_backend == 'event') | ternary('present', 'absent') }}"
+  - name: "mpm_worker"
+    state: "{{ (horizon_apache_mpm_backend == 'worker') | ternary('present', 'absent') }}"
+  - name: "mpm_prefork"
+    state: "{{ (horizon_apache_mpm_backend == 'prefork') | ternary('present', 'absent') }}"
+
 horizon_apache_modules:
   - name: "wsgi"
     state: "present"
   - name: "ssl"
     state: "present"
-  - name: "mpm_event"
-    state: "absent"
-  - name: "mpm_worker"
-    state: "present"
   - name: "rewrite"
     state: "present"
   - name: "headers"