diff --git a/plugin.rb b/plugin.rb
index c8a466e..0f76787 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -103,6 +103,8 @@ after_initialize do
       triggerables %i[topic_tags_changed]
 
       script do |context, fields, automation|
+        next if context["topic"].private_message?
+
         # DiscourseTagging.tag_topic_by_names runs on topic creation and on tags change
         # we only want to send a message when tags change
         next if context["topic"].new_record?
diff --git a/spec/integration/automation_spec.rb b/spec/integration/automation_spec.rb
index 081de47..788a8be 100644
--- a/spec/integration/automation_spec.rb
+++ b/spec/integration/automation_spec.rb
@@ -29,6 +29,8 @@ RSpec.describe "Triggering notifications" do
       SiteSetting.create_tag_allowed_groups = Group::AUTO_GROUPS[:everyone]
       SiteSetting.tag_topic_allowed_groups = Group::AUTO_GROUPS[:everyone]
 
+      SiteSetting.pm_tags_allowed_for_groups = Group::AUTO_GROUPS[:everyone]
+
       automation.upsert_field!(
         "watching_categories",
         "categories",
@@ -84,5 +86,24 @@ RSpec.describe "Triggering notifications" do
       )
       expect(validated_provider.sent_messages.length).to eq(0)
     end
+
+    it "should not trigger notifications for PMs" do
+      automation.upsert_field!(
+        "watching_categories",
+        "categories",
+        { "value" => [nil] },
+        target: "trigger",
+      )
+
+      topic =
+        TopicCreator.create(
+          admin,
+          Guardian.new(admin),
+          valid_attrs.merge(archetype: Archetype.private_message, target_usernames: admin.username),
+        )
+
+      DiscourseTagging.tag_topic_by_names(topic, Guardian.new(admin), [tag.name])
+      expect(validated_provider.sent_messages.length).to eq(0)
+    end
   end
 end