diff --git a/app/models/project.rb b/app/models/project.rb
index 5747eba..c326cf7 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -7,4 +7,6 @@ class Project < ApplicationRecord
   belongs_to :slack_workspace
 
   has_many :developers
+
+  has :related_project, class_name: 'Project', foreign_key: 'related_project_id'
 end
diff --git a/app/services/slack/action/add_code_review.rb b/app/services/slack/action/add_code_review.rb
index 221f94d..3c96ae5 100644
--- a/app/services/slack/action/add_code_review.rb
+++ b/app/services/slack/action/add_code_review.rb
@@ -19,7 +19,11 @@ def initialize(slack_workspace, url, requester, given_reviewers_tags)
         reviewers = given_reviewers
 
         reviewers += pick_reviewers_in_project(reviewers, requester)
-        reviewers += pick_external_reviewers(reviewers, requester)
+
+        related_project = Project.find(project.related_project_id)
+
+        reviewers += pick_external_reviewers_by_project(reviewers, requester, related_project) if related_project.present?
+        reviewers += pick_external_reviewers(reviewers, requester) if related_project.blank?
 
         create_code_review(url, reviewers, given_reviewers, requester)
       rescue ActiveRecord::RecordNotFound => e
@@ -66,6 +70,17 @@ def pick_external_reviewers(reviewers, requester)
           .limit(to_take)
       end
 
+      def pick_external_reviewers_by_project(reviewers, requester, project)
+        to_take = REQUIRED_NUMBER_OF_REVIEWERS - reviewers.length
+
+        Developer
+          .queue
+          .where.not(id: reviewers + [requester])
+          .where(slack_workspace: @slack_workspace)
+          .where(project: project)
+          .limit(to_take)
+      end
+
       def pick_reviewers_by_tags(tags)
         return [] if tags.empty?
 
diff --git a/app/services/slack/action/add_related_project.rb b/app/services/slack/action/add_related_project.rb
new file mode 100644
index 0000000..c93cb9d
--- /dev/null
+++ b/app/services/slack/action/add_related_project.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Slack
+  module Action
+    # Adds a project to another project so that they are related for code reviews
+    class AddRelatedProject < Slack::AbstractAction
+      def initialize(slack_workspace, project_name, related_project_name)
+        super(slack_workspace)
+        project = @slack_workspace.projects.find_by(name: project_name)
+        related_project = @slack_workspace.projects.find_by(name: related_project_name)
+
+        project.related_project_id = related_project.id
+        project.save!
+
+        @text = 'Projects are now related.'
+      end
+    end
+  end
+end
diff --git a/db/migrate/20200221020120_add_related_project_id_to_project.rb b/db/migrate/20200221020120_add_related_project_id_to_project.rb
new file mode 100644
index 0000000..e8a590b
--- /dev/null
+++ b/db/migrate/20200221020120_add_related_project_id_to_project.rb
@@ -0,0 +1,5 @@
+class AddRelatedProjectIdToProject < ActiveRecord::Migration[6.0]
+  def change
+    add_column :projects, :related_project_id, :integer
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 8938be1..be5f384 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_01_24_013912) do
+ActiveRecord::Schema.define(version: 2020_02_21_020120) do
 
   create_table "code_reviews", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "url"
@@ -47,6 +47,7 @@
     t.bigint "slack_workspace_id"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
+    t.integer "related_project_id"
     t.index ["slack_workspace_id"], name: "index_projects_on_slack_workspace_id"
   end