diff --git a/addons/event/models/event.py b/addons/event/models/event.py
index b25f41b783a..6ae4b4c3ee3 100644
--- a/addons/event/models/event.py
+++ b/addons/event/models/event.py
@@ -303,11 +303,10 @@ class EventEvent(models.Model):
     def button_draft(self):
         self.state = 'draft'
 
-    @api.one
+    @api.multi
     def button_cancel(self):
-        for event_reg in self.registration_ids:
-            if event_reg.state == 'done':
-                raise UserError(_("You have already set a registration for this event as 'Attended'. Please reset it to draft if you want to cancel this event."))
+        if any('done' in event.mapped('registration_ids.state') for event in self):
+            raise UserError(_("There are already attendees who attended this event. Please reset it to draft if you want to cancel this event."))
         self.registration_ids.write({'state': 'cancel'})
         self.state = 'cancel'
 
diff --git a/addons/event/views/event_views.xml b/addons/event/views/event_views.xml
index 66208b3da65..29a749fd9e1 100644
--- a/addons/event/views/event_views.xml
+++ b/addons/event/views/event_views.xml
@@ -191,7 +191,8 @@
                         <button string="Confirm Event" name="button_confirm" states="draft" type="object" class="oe_highlight" groups="base.group_user"/>
                         <button string="Finish Event" name="button_done" states="confirm" type="object" class="oe_highlight" groups="base.group_user"/>
                         <button string="Set To Draft" name="button_draft" states="cancel,done" type="object" groups="base.group_user"/>
-                        <button string="Cancel Event" name="button_cancel" states="draft,confirm" type="object" groups="base.group_user"/>
+                        <button string="Cancel Event" name="button_cancel" states="draft,confirm" type="object" groups="base.group_user" attrs="{'invisible': ['|', ('seats_expected', '!=', 0)]}"/>
+                        <button string="Cancel Event" name="button_cancel" states="draft,confirm" type="object" groups="base.group_user" confirm="Are you sure you want to cancel this event? All the linked attendees will be cancelled as well." attrs="{'invisible': ['|', ('seats_expected', '=', 0)]}"/>
                         <field name="state" widget="statusbar" statusbar_visible="draft,confirm,done"/>
                     </header>
                     <sheet>