diff --git a/app/serializers/deployment_entity.rb b/app/serializers/deployment_entity.rb
index 943c707218d..6e91317eb20 100644
--- a/app/serializers/deployment_entity.rb
+++ b/app/serializers/deployment_entity.rb
@@ -18,6 +18,7 @@ class DeploymentEntity < Grape::Entity
   end
 
   expose :created_at
+  expose :finished_at
   expose :tag
   expose :last?
   expose :user, using: UserEntity
diff --git a/app/serializers/deployment_serializer.rb b/app/serializers/deployment_serializer.rb
index 04db6b88489..3fd3e1b9cc8 100644
--- a/app/serializers/deployment_serializer.rb
+++ b/app/serializers/deployment_serializer.rb
@@ -4,7 +4,7 @@ class DeploymentSerializer < BaseSerializer
   entity DeploymentEntity
 
   def represent_concise(resource, opts = {})
-    opts[:only] = [:iid, :id, :sha, :created_at, :tag, :last?, :id, ref: [:name]]
+    opts[:only] = [:iid, :id, :sha, :created_at, :finished_at, :tag, :last?, :id, ref: [:name]]
     represent(resource, opts)
   end
 end
diff --git a/changelogs/unreleased/56130-deployment-date.yml b/changelogs/unreleased/56130-deployment-date.yml
new file mode 100644
index 00000000000..7d1e84bbaa4
--- /dev/null
+++ b/changelogs/unreleased/56130-deployment-date.yml
@@ -0,0 +1,5 @@
+---
+title: Add finished_at to the internal API Deployment entity
+merge_request: 31808
+author:
+type: other
diff --git a/spec/fixtures/api/schemas/deployment.json b/spec/fixtures/api/schemas/deployment.json
index 0828f113495..9216ad0060b 100644
--- a/spec/fixtures/api/schemas/deployment.json
+++ b/spec/fixtures/api/schemas/deployment.json
@@ -3,6 +3,7 @@
   "required": [
     "sha",
     "created_at",
+    "finished_at",
     "iid",
     "tag",
     "last?",
@@ -11,6 +12,7 @@
   ],
   "properties": {
     "created_at": { "type": "string" },
+    "finished_at": { "type": ["string", "null"] },
     "id": { "type": "integer" },
     "iid": { "type": "integer" },
     "last?": { "type": "boolean" },
diff --git a/spec/serializers/deployment_entity_spec.rb b/spec/serializers/deployment_entity_spec.rb
index 76ad2aee5c5..c0ea2b3c389 100644
--- a/spec/serializers/deployment_entity_spec.rb
+++ b/spec/serializers/deployment_entity_spec.rb
@@ -32,6 +32,10 @@ describe DeploymentEntity do
     expect(subject).to include(:created_at)
   end
 
+  it 'exposes finished_at' do
+    expect(subject).to include(:finished_at)
+  end
+
   context 'when the pipeline has another manual action' do
     let(:other_build) { create(:ci_build, :manual, name: 'another deploy', pipeline: pipeline) }
     let!(:other_deployment) { create(:deployment, deployable: other_build) }