diff --git a/mockgen/internal/tests/build_constraint/input.go b/mockgen/internal/tests/build_constraint/input.go
new file mode 100644
index 0000000..009ad7c
--- /dev/null
+++ b/mockgen/internal/tests/build_constraint/input.go
@@ -0,0 +1,5 @@
+package empty_interface
+
+//go:generate mockgen -package empty_interface -destination mock.go -source input.go "-build_constraint=(linux && 386) || (darwin && !cgo) || usertag"
+
+type Empty interface{}
diff --git a/mockgen/internal/tests/build_constraint/mock.go b/mockgen/internal/tests/build_constraint/mock.go
new file mode 100644
index 0000000..7d4dba7
--- /dev/null
+++ b/mockgen/internal/tests/build_constraint/mock.go
@@ -0,0 +1,44 @@
+//go:build (linux && 386) || (darwin && !cgo) || usertag
+
+// Code generated by MockGen. DO NOT EDIT.
+// Source: input.go
+//
+// Generated by this command:
+//
+//	mockgen -package empty_interface -destination mock.go -source input.go -build_constraint=(linux && 386) || (darwin && !cgo) || usertag
+//
+
+// Package empty_interface is a generated GoMock package.
+package empty_interface
+
+import (
+	gomock "go.uber.org/mock/gomock"
+)
+
+// MockEmpty is a mock of Empty interface.
+type MockEmpty struct {
+	ctrl     *gomock.Controller
+	recorder *MockEmptyMockRecorder
+}
+
+// MockEmptyMockRecorder is the mock recorder for MockEmpty.
+type MockEmptyMockRecorder struct {
+	mock *MockEmpty
+}
+
+// NewMockEmpty creates a new mock instance.
+func NewMockEmpty(ctrl *gomock.Controller) *MockEmpty {
+	mock := &MockEmpty{ctrl: ctrl}
+	mock.recorder = &MockEmptyMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockEmpty) EXPECT() *MockEmptyMockRecorder {
+	return m.recorder
+}
+
+// ISGOMOCK indicates that this struct is a gomock mock.
+func (m *MockEmpty) ISGOMOCK() struct{} {
+	return struct{}{}
+}
diff --git a/mockgen/mockgen.go b/mockgen/mockgen.go
index 6d7634b..7e2fe25 100644
--- a/mockgen/mockgen.go
+++ b/mockgen/mockgen.go
@@ -64,6 +64,7 @@ var (
 	writeSourceComment     = flag.Bool("write_source_comment", true, "Writes original file (source mode) or interface names (reflect mode) comment if true.")
 	writeGenerateDirective = flag.Bool("write_generate_directive", false, "Add //go:generate directive to regenerate the mock")
 	copyrightFile          = flag.String("copyright_file", "", "Copyright file used to add copyright header")
+	buildConstraint        = flag.String("build_constraint", "", "If non-empty, added as //go:build <constraint>")
 	typed                  = flag.Bool("typed", false, "Generate Type-safe 'Return', 'Do', 'DoAndReturn' function")
 	imports                = flag.String("imports", "", "(source mode) Comma-separated name=path pairs of explicit imports to use.")
 	auxFiles               = flag.String("aux_files", "", "(source mode) Comma-separated pkg=path pairs of auxiliary Go source files.")
@@ -143,7 +144,9 @@ func main() {
 		}
 	}
 
-	g := new(generator)
+	g := &generator{
+		buildConstraint: *buildConstraint,
+	}
 	if *source != "" {
 		g.filename = *source
 	} else {
@@ -251,6 +254,7 @@ type generator struct {
 	destination               string            // may be empty
 	srcPackage, srcInterfaces string            // may be empty
 	copyrightHeader           string
+	buildConstraint           string // may be empty
 
 	packageMap map[string]string // map from import path to package name
 }
@@ -306,6 +310,12 @@ func (g *generator) Generate(pkg *model.Package, outputPkgName string, outputPac
 		g.p("")
 	}
 
+	if g.buildConstraint != "" {
+		g.p("//go:build %s", g.buildConstraint)
+		// https://pkg.go.dev/cmd/go#hdr-Build_constraints:~:text=a%20build%20constraint%20should%20be%20followed%20by%20a%20blank%20line
+		g.p("")
+	}
+
 	g.p("// Code generated by MockGen. DO NOT EDIT.")
 	if *writeSourceComment {
 		if g.filename != "" {