diff --git a/lib/pact_broker/api/resources/can_i_deploy.rb b/lib/pact_broker/api/resources/can_i_deploy.rb
index 511aea209..a262cd0b1 100644
--- a/lib/pact_broker/api/resources/can_i_deploy.rb
+++ b/lib/pact_broker/api/resources/can_i_deploy.rb
@@ -1,11 +1,14 @@
 require 'pact_broker/api/resources/matrix'
 require 'pact_broker/matrix/can_i_deploy_query_schema'
 require 'pact_broker/matrix/parse_can_i_deploy_query'
+require 'pact_broker/messages'
 
 module PactBroker
   module Api
     module Resources
       class CanIDeploy < Matrix
+        include PactBroker::Messages
+
         def initialize
           super
           @query_params = JSON.parse(Rack::Utils.parse_nested_query(request.uri.query).to_json, symbolize_names: true)
@@ -16,6 +19,9 @@ def malformed_request?
           if (errors = query_schema.call(query_params)).any?
             set_json_validation_error_messages(errors)
             true
+          elsif !pacticipant
+            set_json_validation_error_messages(pacticipant: [message('errors.validation.pacticipant_not_found', name: pacticipant_name)])
+            true
           else
             false
           end
@@ -32,6 +38,14 @@ def policy_name
         def query_schema
           PactBroker::Api::Contracts::CanIDeployQuerySchema
         end
+
+        def pacticipant
+          @pacticipant ||= pacticipant_service.find_pacticipant_by_name(pacticipant_name)
+        end
+
+        def pacticipant_name
+          selectors.first.pacticipant_name
+        end
       end
     end
   end
diff --git a/lib/pact_broker/locale/en.yml b/lib/pact_broker/locale/en.yml
index 222d32b27..529201932 100644
--- a/lib/pact_broker/locale/en.yml
+++ b/lib/pact_broker/locale/en.yml
@@ -45,6 +45,7 @@ en:
         pacticipant_name_mismatch: "in pact ('%{name_in_pact}') does not match %{pacticipant} name in path ('%{name}')."
         connection_encoding_not_utf8: "The Sequel connection encoding (%{encoding}) is strongly recommended to be \"utf8\". If you need to set it to %{encoding} for some particular reason, then disable this check by setting config.validate_database_connection_config = false"
         invalid_webhook_uuid: The UUID can only contain the characters A-Z, a-z, 0-9, _ and -, and must be 16 or more characters.
+        pacticipant_not_found: No pacticipant with name '%{name}' found
       duplicate_pacticipant: |
         This is the first time a pact has been published for "%{new_name}".
         The name "%{new_name}" is very similar to the following existing consumers/providers:
diff --git a/spec/lib/pact_broker/api/resources/can_i_deploy_spec.rb b/spec/lib/pact_broker/api/resources/can_i_deploy_spec.rb
new file mode 100644
index 000000000..90ef2a20c
--- /dev/null
+++ b/spec/lib/pact_broker/api/resources/can_i_deploy_spec.rb
@@ -0,0 +1,51 @@
+require 'pact_broker/api/resources/can_i_deploy'
+
+module PactBroker
+  module Api
+    module Resources
+      describe CanIDeploy do
+        include_context "stubbed services"
+
+        before do
+          allow(pacticipant_service).to receive(:find_pacticipant_by_name).and_return(pacticipant)
+          allow(matrix_service).to receive(:find).and_return(results)
+          allow_any_instance_of(described_class).to receive(:matrix_service).and_return(matrix_service)
+          allow(PactBroker::Api::Decorators::MatrixDecorator).to receive(:new).and_return(decorator)
+        end
+
+        let(:results) { double('results') }
+        let(:pacticipant) { double('pacticipant') }
+        let(:decorator) { instance_double('PactBroker::Api::Decorators::MatrixDecorator', to_json: 'response_body') }
+        let(:matrix_service) { class_double("PactBroker::Matrix::Service").as_stubbed_const }
+
+        let(:query) do
+          {
+            pacticipant: "Foo",
+            version: "1.2.3",
+            to: "prod"
+          }
+        end
+
+        subject { get("/can-i-deploy", query, { 'HTTP_ACCEPT' => 'application/hal+json'}) }
+
+        context "with the wrong query" do
+          let(:query) { {} }
+
+          it "returns a 400" do
+            expect(subject.status).to eq 400
+            expect(JSON.parse(subject.body)["errors"]["pacticipant"].first).to_not be_empty
+          end
+        end
+
+        context "when the pacticipant does not exist" do
+          let(:pacticipant) { nil }
+
+          it "returns a 400" do
+            expect(subject.status).to eq 400
+            expect(JSON.parse(subject.body)["errors"]["pacticipant"].first).to match /Foo.*found/
+          end
+        end
+      end
+    end
+  end
+end