diff --git a/apis/v1alpha2/grpcroute_types.go b/apis/v1alpha2/grpcroute_types.go
index dcb501f78e..2d0aa11aac 100644
--- a/apis/v1alpha2/grpcroute_types.go
+++ b/apis/v1alpha2/grpcroute_types.go
@@ -223,8 +223,8 @@ type GRPCRouteRule struct {
 	// - Implementation-specific custom filters have no API guarantees across
 	//   implementations.
 	//
-	// Specifying a core filter multiple times has unspecified or
-	// implementation-specific conformance.
+	// Specifying the same filter multiple times is not supported unless explicitly
+	// indicated in the filter.
 	//
 	// If an implementation can not support a combinations of filters, they must clearly
 	// document that limitation. In cases where incompatible or unsupported
@@ -515,6 +515,10 @@ type GRPCRouteFilter struct {
 	// Requests are sent to the specified destination, but responses from
 	// that destination are ignored.
 	//
+	// This filter can be used multiple times within the same rule. Note that
+	// not all implementations will be able to support mirroring to multiple
+	// backends.
+	//
 	// Support: Extended
 	//
 	// +optional
@@ -527,6 +531,7 @@ type GRPCRouteFilter struct {
 	//
 	// Support: Implementation-specific
 	//
+	// This filter can be used multiple times within the same rule.
 	// +optional
 	ExtensionRef *LocalObjectReference `json:"extensionRef,omitempty"`
 }
diff --git a/apis/v1alpha2/validation/grpcroute.go b/apis/v1alpha2/validation/grpcroute.go
index 62ed859235..d7e452d41c 100644
--- a/apis/v1alpha2/validation/grpcroute.go
+++ b/apis/v1alpha2/validation/grpcroute.go
@@ -32,6 +32,7 @@ var (
 	// repeated multiple times in a rule.
 	repeatableGRPCRouteFilters = []gatewayv1a2.GRPCRouteFilterType{
 		gatewayv1a2.GRPCRouteFilterExtensionRef,
+		gatewayv1a2.GRPCRouteFilterRequestMirror,
 	}
 	validServiceName      = `^(?i)\.?[a-z_][a-z_0-9]*(\.[a-z_][a-z_0-9]*)*$`
 	validServiceNameRegex = regexp.MustCompile(validServiceName)
@@ -165,7 +166,7 @@ func validateGRPCRouteFilters(filters []gatewayv1a2.GRPCRouteFilter, path *field
 		}
 		errs = append(errs, validateGRPCRouteFilterType(filter, path.Index(i))...)
 	}
-	// custom filters don't have any validation
+	// repeatableGRPCRouteFilters filters can be used more than once
 	for _, key := range repeatableGRPCRouteFilters {
 		delete(counts, key)
 	}
diff --git a/apis/v1alpha2/validation/grpcroute_test.go b/apis/v1alpha2/validation/grpcroute_test.go
index 9055864b3f..a7c1c8fac4 100644
--- a/apis/v1alpha2/validation/grpcroute_test.go
+++ b/apis/v1alpha2/validation/grpcroute_test.go
@@ -236,10 +236,38 @@ func TestValidateGRPCRoute(t *testing.T) {
 					}},
 				},
 			},
+		},
+		{
+			name: "invalid GRPCRoute with duplicate RequestHeaderModifier filters",
+			rules: []gatewayv1a2.GRPCRouteRule{
+				{
+					Filters: []gatewayv1a2.GRPCRouteFilter{{
+						Type: "RequestHeaderModifier",
+						RequestHeaderModifier: &gatewayv1a2.HTTPHeaderFilter{
+							Set: []gatewayv1a2.HTTPHeader{
+								{
+									Name:  "special-header",
+									Value: "foo",
+								},
+							},
+						},
+					}, {
+						Type: "RequestHeaderModifier",
+						RequestHeaderModifier: &gatewayv1a2.HTTPHeaderFilter{
+							Add: []gatewayv1a2.HTTPHeader{
+								{
+									Name:  "my-header",
+									Value: "bar",
+								},
+							},
+						},
+					}},
+				},
+			},
 			errs: field.ErrorList{
 				{
 					Type:     field.ErrorTypeInvalid,
-					BadValue: "RequestMirror",
+					BadValue: "RequestHeaderModifier",
 					Field:    "spec.rules[0].filters",
 					Detail:   "cannot be used multiple times in the same rule",
 				},
@@ -305,8 +333,8 @@ func TestValidateGRPCBackendUniqueFilters(t *testing.T) {
 			},
 		}},
 	}, {
-		name:     "invalid grpcRoute Rules duplicate mirror filter",
-		errCount: 1,
+		name:     "valid grpcRoute Rules duplicate mirror filter",
+		errCount: 0,
 		rules: []gatewayv1a2.GRPCRouteRule{{
 			BackendRefs: []gatewayv1a2.GRPCBackendRef{
 				{
diff --git a/config/crd/experimental/gateway.networking.k8s.io_grpcroutes.yaml b/config/crd/experimental/gateway.networking.k8s.io_grpcroutes.yaml
index bc42220b70..d927fd2fd1 100644
--- a/config/crd/experimental/gateway.networking.k8s.io_grpcroutes.yaml
+++ b/config/crd/experimental/gateway.networking.k8s.io_grpcroutes.yaml
@@ -331,7 +331,9 @@ spec:
                                     extension to the \"filter\" behavior.  For example,
                                     resource \"myroutefilter\" in group \"networking.example.net\").
                                     ExtensionRef MUST NOT be used for core and extended
-                                    filters. \n Support: Implementation-specific"
+                                    filters. \n Support: Implementation-specific \n
+                                    This filter can be used multiple times within
+                                    the same rule."
                                   properties:
                                     group:
                                       description: Group is the group of the referent.
@@ -469,7 +471,10 @@ spec:
                                   description: "RequestMirror defines a schema for
                                     a filter that mirrors requests. Requests are sent
                                     to the specified destination, but responses from
-                                    that destination are ignored. \n Support: Extended"
+                                    that destination are ignored. \n This filter can
+                                    be used multiple times within the same rule. Note
+                                    that not all implementations will be able to support
+                                    mirroring to multiple backends. \n Support: Extended"
                                   properties:
                                     backendRef:
                                       description: "BackendRef references a resource
@@ -793,8 +798,8 @@ spec:
                         all implementations that support GRPCRoute. - Implementers
                         are encouraged to support extended filters. - Implementation-specific
                         custom filters have no API guarantees across implementations.
-                        \n Specifying a core filter multiple times has unspecified
-                        or implementation-specific conformance. \n If an implementation
+                        \n Specifying the same filter multiple times is not supported
+                        unless explicitly indicated in the filter. \n If an implementation
                         can not support a combinations of filters, they must clearly
                         document that limitation. In cases where incompatible or unsupported
                         filters are specified and cause the `Accepted` condition to
@@ -815,7 +820,8 @@ spec:
                               extension to the \"filter\" behavior.  For example,
                               resource \"myroutefilter\" in group \"networking.example.net\").
                               ExtensionRef MUST NOT be used for core and extended
-                              filters. \n Support: Implementation-specific"
+                              filters. \n Support: Implementation-specific \n This
+                              filter can be used multiple times within the same rule."
                             properties:
                               group:
                                 description: Group is the group of the referent. For
@@ -945,7 +951,10 @@ spec:
                             description: "RequestMirror defines a schema for a filter
                               that mirrors requests. Requests are sent to the specified
                               destination, but responses from that destination are
-                              ignored. \n Support: Extended"
+                              ignored. \n This filter can be used multiple times within
+                              the same rule. Note that not all implementations will
+                              be able to support mirroring to multiple backends. \n
+                              Support: Extended"
                             properties:
                               backendRef:
                                 description: "BackendRef references a resource where