diff --git a/pkg/api/types.go b/pkg/api/types.go
index 2d446df5c51..50b3b1b85ce 100644
--- a/pkg/api/types.go
+++ b/pkg/api/types.go
@@ -111,7 +111,7 @@ type Port struct {
 	HostPort int `yaml:"hostPort,omitempty" json:"hostPort,omitempty"`
 	// Required: This must be a valid port number, 0 < x < 65536.
 	ContainerPort int `yaml:"containerPort" json:"containerPort"`
-	// Optional: Defaults to "TCP".
+	// Optional: Supports "TCP" and "UDP".  Defaults to "TCP".
 	Protocol string `yaml:"protocol,omitempty" json:"protocol,omitempty"`
 	// Optional: What host IP to bind the external port to.
 	HostIP string `yaml:"hostIP,omitempty" json:"hostIP,omitempty"`
@@ -389,7 +389,11 @@ func (*ServiceList) IsAnAPIObject() {}
 // will answer requests sent through the proxy.
 type Service struct {
 	JSONBase `json:",inline" yaml:",inline"`
-	Port     int `json:"port,omitempty" yaml:"port,omitempty"`
+
+	// Required.
+	Port int `json:"port" yaml:"port"`
+	// Optional: Supports "TCP" and "UDP".  Defaults to "TCP".
+	Protocol string `yaml:"protocol,omitempty" json:"protocol,omitempty"`
 
 	// This service's labels.
 	Labels map[string]string `json:"labels,omitempty" yaml:"labels,omitempty"`
diff --git a/pkg/api/v1beta1/types.go b/pkg/api/v1beta1/types.go
index 552f61f2c28..1dba02b5f47 100644
--- a/pkg/api/v1beta1/types.go
+++ b/pkg/api/v1beta1/types.go
@@ -111,7 +111,7 @@ type Port struct {
 	HostPort int `yaml:"hostPort,omitempty" json:"hostPort,omitempty"`
 	// Required: This must be a valid port number, 0 < x < 65536.
 	ContainerPort int `yaml:"containerPort" json:"containerPort"`
-	// Optional: Defaults to "TCP".
+	// Optional: Supports "TCP" and "UDP".  Defaults to "TCP".
 	Protocol string `yaml:"protocol,omitempty" json:"protocol,omitempty"`
 	// Optional: What host IP to bind the external port to.
 	HostIP string `yaml:"hostIP,omitempty" json:"hostIP,omitempty"`
@@ -401,7 +401,11 @@ func (*ServiceList) IsAnAPIObject() {}
 // will answer requests sent through the proxy.
 type Service struct {
 	JSONBase `json:",inline" yaml:",inline"`
-	Port     int `json:"port,omitempty" yaml:"port,omitempty"`
+
+	// Required.
+	Port int `json:"port" yaml:"port"`
+	// Optional: Supports "TCP" and "UDP".  Defaults to "TCP".
+	Protocol string `yaml:"protocol,omitempty" json:"protocol,omitempty"`
 
 	// This service's labels.
 	Labels map[string]string `json:"labels,omitempty" yaml:"labels,omitempty"`
diff --git a/pkg/api/validation/validation.go b/pkg/api/validation/validation.go
index 48f183b4162..7743cdd4b78 100644
--- a/pkg/api/validation/validation.go
+++ b/pkg/api/validation/validation.go
@@ -282,6 +282,11 @@ func ValidateService(service *api.Service) errs.ErrorList {
 	if !util.IsValidPortNum(service.Port) {
 		allErrs = append(allErrs, errs.NewFieldInvalid("Service.Port", service.Port))
 	}
+	if len(service.Protocol) == 0 {
+		service.Protocol = "TCP"
+	} else if !supportedPortProtocols.Has(strings.ToUpper(service.Protocol)) {
+		allErrs = append(allErrs, errs.NewFieldNotSupported("protocol", service.Protocol))
+	}
 	if labels.Set(service.Selector).AsSelector().Empty() {
 		allErrs = append(allErrs, errs.NewFieldRequired("selector", service.Selector))
 	}
diff --git a/pkg/api/validation/validation_test.go b/pkg/api/validation/validation_test.go
index 1f1cc8b72c2..e977fc1a6f1 100644
--- a/pkg/api/validation/validation_test.go
+++ b/pkg/api/validation/validation_test.go
@@ -408,6 +408,17 @@ func TestValidateService(t *testing.T) {
 			// Should fail because the port number is invalid.
 			numErrs: 1,
 		},
+		{
+			name: "invalid protocol",
+			svc: api.Service{
+				JSONBase: api.JSONBase{ID: "abc123"},
+				Port:     8675,
+				Protocol: "INVALID",
+				Selector: map[string]string{"foo": "bar"},
+			},
+			// Should fail because the protocol is invalid.
+			numErrs: 1,
+		},
 		{
 			name: "missing selector",
 			svc: api.Service{
@@ -422,6 +433,7 @@ func TestValidateService(t *testing.T) {
 			svc: api.Service{
 				JSONBase: api.JSONBase{ID: "abc123"},
 				Port:     1,
+				Protocol: "TCP",
 				Selector: map[string]string{"foo": "bar"},
 			},
 			numErrs: 0,
@@ -431,6 +443,7 @@ func TestValidateService(t *testing.T) {
 			svc: api.Service{
 				JSONBase: api.JSONBase{ID: "abc123"},
 				Port:     65535,
+				Protocol: "UDP",
 				Selector: map[string]string{"foo": "bar"},
 			},
 			numErrs: 0,
@@ -452,6 +465,19 @@ func TestValidateService(t *testing.T) {
 			t.Errorf("Unexpected error list for case %q: %+v", tc.name, errs)
 		}
 	}
+
+	svc := api.Service{
+		Port:     6502,
+		JSONBase: api.JSONBase{ID: "foo"},
+		Selector: map[string]string{"foo": "bar"},
+	}
+	errs := ValidateService(&svc)
+	if len(errs) != 0 {
+		t.Errorf("Unexpected non-zero error list: %#v", errs)
+	}
+	if svc.Protocol != "TCP" {
+		t.Errorf("Expected default protocol of 'TCP': %#v", errs)
+	}
 }
 
 func TestValidateReplicationController(t *testing.T) {