diff --git a/README.md b/README.md
index f4ada07..67873bf 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,8 @@ moq [flags] source-dir interface [interface2 [interface3 [...]]]
 		go pretty-printer: gofmt, goimports or noop (default gofmt)
 	-out string
 		output file (default stdout)
+	-out-dir string
+		output dir (exclusive with -out)
 	-pkg string
 		package name (default will infer)
 	-stub
diff --git a/main.go b/main.go
index 89adb3d..1699d95 100644
--- a/main.go
+++ b/main.go
@@ -18,6 +18,7 @@ var Version string = "dev"
 
 type userFlags struct {
 	outFile    string
+	outDir     string
 	pkgName    string
 	formatter  string
 	stubImpl   bool
@@ -30,6 +31,7 @@ type userFlags struct {
 func main() {
 	var flags userFlags
 	flag.StringVar(&flags.outFile, "out", "", "output file (default stdout)")
+	flag.StringVar(&flags.outDir, "out-dir", "", "output dir (exclusive with -out)")
 	flag.StringVar(&flags.pkgName, "pkg", "", "package name (default will infer)")
 	flag.StringVar(&flags.formatter, "fmt", "", "go pretty-printer: gofmt, goimports or noop (default gofmt)")
 	flag.BoolVar(&flags.stubImpl, "stub", false,
@@ -76,12 +78,6 @@ func run(flags userFlags) error {
 		}
 	}
 
-	var buf bytes.Buffer
-	var out io.Writer = os.Stdout
-	if flags.outFile != "" {
-		out = &buf
-	}
-
 	srcDir, args := flags.args[0], flags.args[1:]
 	m, err := moq.New(moq.Config{
 		SrcDir:     srcDir,
@@ -95,19 +91,52 @@ func run(flags userFlags) error {
 		return err
 	}
 
-	if err = m.Mock(out, args...); err != nil {
+	switch {
+	case flags.outDir != "" && flags.outFile != "":
+		return errors.New("use only one  of the flags -out and -out-dir")
+	case flags.outDir != "":
+		return mockToDir(m, flags.outDir, args...)
+	case flags.outFile != "":
+		return mockToFile(m, flags.outFile, args...)
+	default:
+		// mock to stdout
+		return m.Mock(os.Stdout, args...)
+	}
+}
+
+func mockToDir(m *moq.Mocker, outDir string, args ...string) error {
+	if err := os.MkdirAll(outDir, 0o750); err != nil {
 		return err
 	}
 
-	if flags.outFile == "" {
-		return nil
+	var buf bytes.Buffer
+	for _, arg := range args {
+		if err := m.Mock(&buf, arg); err != nil {
+			return err
+		}
+
+		filename := filepath.Join(outDir, m.FileMockName(arg))
+		if err := ioutil.WriteFile(filename, buf.Bytes(), 0o600); err != nil {
+			return err
+		}
+
+		buf.Reset()
 	}
 
-	// create the file
-	err = os.MkdirAll(filepath.Dir(flags.outFile), 0o750)
-	if err != nil {
+	return nil
+}
+
+func mockToFile(m *moq.Mocker, outFile string, args ...string) error {
+	var buf bytes.Buffer
+	var out io.Writer = &buf
+
+	if err := m.Mock(out, args...); err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(outFile), 0o750); err != nil {
 		return err
 	}
 
-	return ioutil.WriteFile(flags.outFile, buf.Bytes(), 0o600)
+	return ioutil.WriteFile(outFile, buf.Bytes(), 0o600)
 }
diff --git a/pkg/moq/moq.go b/pkg/moq/moq.go
index e8a2975..c7379ff 100644
--- a/pkg/moq/moq.go
+++ b/pkg/moq/moq.go
@@ -7,6 +7,7 @@ import (
 	"go/types"
 	"io"
 	"strings"
+	"unicode"
 
 	"github.com/matryer/moq/internal/registry"
 	"github.com/matryer/moq/internal/template"
@@ -114,6 +115,19 @@ func (m *Mocker) Mock(w io.Writer, namePairs ...string) error {
 	return nil
 }
 
+// FileMockName generates file name for mock from interface
+func (m *Mocker) FileMockName(namePair string) string {
+	ifaceName, mockName := parseInterfaceName(namePair)
+
+	var mockFile string
+	if strings.HasPrefix(mockName, ifaceName) {
+		mockFile = toSnakeCase(ifaceName)
+	} else {
+		mockFile = toSnakeCase(mockName)
+	}
+	return mockFile + ".go"
+}
+
 func (m *Mocker) typeParams(tparams *types.TypeParamList) []template.TypeParamData {
 	var tpd []template.TypeParamData
 	if tparams == nil {
@@ -210,3 +224,49 @@ func parseInterfaceName(namePair string) (ifaceName, mockName string) {
 	ifaceName = parts[0]
 	return ifaceName, ifaceName + "Mock"
 }
+
+func toSnakeCase(name string) string {
+	var buf bytes.Buffer
+
+	fUpper := -1
+	for i, r := range name {
+		if unicode.IsUpper(r) {
+			if fUpper < 0 {
+				fUpper = i
+			}
+			continue
+		}
+
+		if fUpper < 0 {
+			// just next low rune
+			buf.WriteRune(r)
+			continue
+		}
+
+		if fUpper == 0 && name[0] == 'I' {
+			// special case for interface preffix
+			buf.WriteString("i")
+			fUpper++
+		}
+		if fUpper > 0 {
+			buf.WriteRune('_')
+		}
+		if i-fUpper >= 2 {
+			buf.WriteString(strings.ToLower(name[fUpper : i-1]))
+			buf.WriteRune('_')
+		}
+
+		buf.WriteString(strings.ToLower(name[i-1 : i]))
+		buf.WriteRune(r)
+		fUpper = -1
+	}
+
+	if fUpper > 0 {
+		buf.WriteRune('_')
+	}
+
+	if fUpper >= 0 {
+		buf.WriteString(strings.ToLower(name[fUpper:]))
+	}
+	return buf.String()
+}
diff --git a/pkg/moq/moq_test.go b/pkg/moq/moq_test.go
index 7dceb8f..0320972 100644
--- a/pkg/moq/moq_test.go
+++ b/pkg/moq/moq_test.go
@@ -699,6 +699,31 @@ func TestMockError(t *testing.T) {
 	}
 }
 
+func TestToSnakeCase(t *testing.T) {
+	cases := []struct {
+		arg, want string
+	}{
+		{"allcased", "allcased"},
+		{"ALLUPPER", "allupper"},
+		{"ICache", "i_cache"},
+		{"IJournalService", "i_journal_service"},
+		{"ITJournalService", "i_t_journal_service"},
+		{"IAddressAPI", "i_address_api"},
+		{"IABClient", "i_ab_client"},
+		{"APIClient", "api_client"},
+		{"IAPIClient", "i_api_client"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.arg, func(t *testing.T) {
+			actual := toSnakeCase(tc.arg)
+			if actual != tc.want {
+				t.Errorf("expect: %v, actual: %v", tc.want, actual)
+			}
+		})
+	}
+}
+
 // normalize normalizes \r\n (windows) and \r (mac)
 // into \n (unix)
 func normalize(d []byte) []byte {