diff --git a/cmd/libs/go2idl/conversion-gen/generators/conversion.go b/cmd/libs/go2idl/conversion-gen/generators/conversion.go
index 026a9a33cda..83ea0e7dd46 100644
--- a/cmd/libs/go2idl/conversion-gen/generators/conversion.go
+++ b/cmd/libs/go2idl/conversion-gen/generators/conversion.go
@@ -46,13 +46,26 @@ type CustomArgs struct {
 	SkipUnsafe bool
 }
 
-// This is the comment tag that carries parameters for conversion generation.
-const tagName = "k8s:conversion-gen"
+// These are the comment tags that carry parameters for conversion generation.
+const (
+	// e.g., "+k8s:conversion-gen=<peer-pkg>" in doc.go, where <peer-pkg> is the
+	// import path of the package the peer types are defined in.
+	// e.g., "+k8s:conversion-gen=false" in a type's comment will let
+	// conversion-gen skip that type.
+	tagName = "k8s:conversion-gen"
+	// e.g., "+k8s:conversion-gen-external-types=<type-pkg>" in doc.go, where
+	// <type-pkg> is the relative path to the package the types are defined in.
+	externalTypesTagName = "k8s:conversion-gen-external-types"
+)
 
 func extractTag(comments []string) []string {
 	return types.ExtractCommentTags("+", comments)[tagName]
 }
 
+func extractExternalTypesTag(comments []string) []string {
+	return types.ExtractCommentTags("+", comments)[externalTypesTagName]
+}
+
 func isCopyOnly(comments []string) bool {
 	values := types.ExtractCommentTags("+", comments)["k8s:conversion-fn"]
 	return len(values) == 1 && values[0] == "copy-only"
@@ -198,6 +211,10 @@ func Packages(context *generator.Context, arguments *args.GeneratorArgs) generat
 	for i := range inputs {
 		glog.V(5).Infof("considering pkg %q", i)
 		pkg := context.Universe[i]
+		// typesPkg is where the versioned types are defined. Sometimes it is
+		// different from pkg. For example, kubernetes core/v1 types are defined
+		// in vendor/k8s.io/api/core/v1, while pkg is at pkg/api/v1.
+		typesPkg := pkg
 		if pkg == nil {
 			// If the input had no Go files, for example.
 			continue
@@ -224,6 +241,24 @@ func Packages(context *generator.Context, arguments *args.GeneratorArgs) generat
 			skipUnsafe = customArgs.SkipUnsafe
 		}
 
+		// if the external types are not in the same package where the conversion functions to be generated
+		externalTypesValues := extractExternalTypesTag(pkg.Comments)
+		if externalTypesValues != nil {
+			if len(externalTypesValues) != 1 {
+				glog.Fatalf("  expect only one value for %q tag, got: %q", externalTypesTagName, externalTypesValues)
+			}
+			externalTypes := externalTypesValues[0]
+			glog.V(5).Infof("  external types tags: %q", externalTypes)
+			var err error
+			typesPkg, err = context.AddDirectory(filepath.Join(pkg.Path, externalTypes))
+			if err != nil {
+				glog.Fatalf("cannot import package %s", externalTypes)
+			}
+			// update context.Order to the latest context.Universe
+			orderer := namer.Orderer{Namer: namer.NewPublicNamer(1)}
+			context.Order = orderer.OrderUniverse(context.Universe)
+		}
+
 		// if the source path is within a /vendor/ directory (for example,
 		// k8s.io/kubernetes/vendor/k8s.io/apimachinery/pkg/apis/meta/v1), allow
 		// generation to output to the proper relative path (under vendor).
@@ -263,11 +298,11 @@ func Packages(context *generator.Context, arguments *args.GeneratorArgs) generat
 				HeaderText:  header,
 				GeneratorFunc: func(c *generator.Context) (generators []generator.Generator) {
 					return []generator.Generator{
-						NewGenConversion(arguments.OutputFileBaseName, pkg.Path, manualConversions, peerPkgs, unsafeEquality),
+						NewGenConversion(arguments.OutputFileBaseName, typesPkg.Path, pkg.Path, manualConversions, peerPkgs, unsafeEquality),
 					}
 				},
 				FilterFunc: func(c *generator.Context, t *types.Type) bool {
-					return t.Name.Package == pkg.Path
+					return t.Name.Package == typesPkg.Path
 				},
 			})
 	}
@@ -380,7 +415,12 @@ type TypesEqual interface {
 // genConversion produces a file with a autogenerated conversions.
 type genConversion struct {
 	generator.DefaultGen
-	targetPackage     string
+	// the package that contains the types that conversion func are going to be
+	// generated for
+	typesPackage string
+	// the package that the conversion funcs are going to be output to
+	outputPackage string
+	// packages that contain the peer of types in typesPacakge
 	peerPackages      []string
 	manualConversions conversionFuncMap
 	imports           namer.ImportTracker
@@ -389,12 +429,13 @@ type genConversion struct {
 	useUnsafe         TypesEqual
 }
 
-func NewGenConversion(sanitizedName, targetPackage string, manualConversions conversionFuncMap, peerPkgs []string, useUnsafe TypesEqual) generator.Generator {
+func NewGenConversion(sanitizedName, typesPackage, outputPackage string, manualConversions conversionFuncMap, peerPkgs []string, useUnsafe TypesEqual) generator.Generator {
 	return &genConversion{
 		DefaultGen: generator.DefaultGen{
 			OptionalName: sanitizedName,
 		},
-		targetPackage:     targetPackage,
+		typesPackage:      typesPackage,
+		outputPackage:     outputPackage,
 		peerPackages:      peerPkgs,
 		manualConversions: manualConversions,
 		imports:           generator.NewImportTracker(),
@@ -407,7 +448,7 @@ func NewGenConversion(sanitizedName, targetPackage string, manualConversions con
 func (g *genConversion) Namers(c *generator.Context) namer.NameSystems {
 	// Have the raw namer for this file track what it imports.
 	return namer.NameSystems{
-		"raw": namer.NewRawNamer(g.targetPackage, g.imports),
+		"raw": namer.NewRawNamer(g.outputPackage, g.imports),
 		"publicIT": &namerPlusImportTracking{
 			delegate: conversionNamer(),
 			tracker:  g.imports,
@@ -428,13 +469,13 @@ func (n *namerPlusImportTracking) Name(t *types.Type) string {
 func (g *genConversion) convertibleOnlyWithinPackage(inType, outType *types.Type) bool {
 	var t *types.Type
 	var other *types.Type
-	if inType.Name.Package == g.targetPackage {
+	if inType.Name.Package == g.typesPackage {
 		t, other = inType, outType
 	} else {
 		t, other = outType, inType
 	}
 
-	if t.Name.Package != g.targetPackage {
+	if t.Name.Package != g.typesPackage {
 		return false
 	}
 	// If the type has opted out, skip it.
@@ -471,10 +512,10 @@ func (g *genConversion) Filter(c *generator.Context, t *types.Type) bool {
 }
 
 func (g *genConversion) isOtherPackage(pkg string) bool {
-	if pkg == g.targetPackage {
+	if pkg == g.outputPackage {
 		return false
 	}
-	if strings.HasSuffix(pkg, `"`+g.targetPackage+`"`) {
+	if strings.HasSuffix(pkg, `"`+g.outputPackage+`"`) {
 		return false
 	}
 	return true