diff --git a/weed/command/s3.go b/weed/command/s3.go
index f2dffd57e..dc943b23d 100644
--- a/weed/command/s3.go
+++ b/weed/command/s3.go
@@ -3,7 +3,9 @@ package command
 import (
 	"context"
 	"crypto/tls"
+	"crypto/x509"
 	"fmt"
+	"io/ioutil"
 	"net"
 	"net/http"
 	"os"
@@ -42,6 +44,8 @@ type S3Options struct {
 	domainName                *string
 	tlsPrivateKey             *string
 	tlsCertificate            *string
+	tlsCACertificate          *string
+	tlsVerifyClientCert       *bool
 	metricsHttpPort           *int
 	allowEmptyFolder          *bool
 	allowDeleteBucketNotEmpty *bool
@@ -65,6 +69,8 @@ func init() {
 	s3StandaloneOptions.auditLogConfig = cmdS3.Flag.String("auditLogConfig", "", "path to the audit log config file")
 	s3StandaloneOptions.tlsPrivateKey = cmdS3.Flag.String("key.file", "", "path to the TLS private key file")
 	s3StandaloneOptions.tlsCertificate = cmdS3.Flag.String("cert.file", "", "path to the TLS certificate file")
+	s3StandaloneOptions.tlsCACertificate = cmdS3.Flag.String("cacert.file", "", "path to the TLS CA certificate file")
+	s3StandaloneOptions.tlsVerifyClientCert = cmdS3.Flag.Bool("tlsVerifyClientCert", false, "whether to verify the client's certificate")
 	s3StandaloneOptions.metricsHttpPort = cmdS3.Flag.Int("metricsPort", 0, "Prometheus metrics listen port")
 	s3StandaloneOptions.allowEmptyFolder = cmdS3.Flag.Bool("allowEmptyFolder", true, "allow empty folders")
 	s3StandaloneOptions.allowDeleteBucketNotEmpty = cmdS3.Flag.Bool("allowDeleteBucketNotEmpty", true, "allow recursive deleting all entries along with bucket")
@@ -289,7 +295,27 @@ func (s3opt *S3Options) startS3Server() bool {
 		if s3opt.certProvider, err = pemfile.NewProvider(pemfileOptions); err != nil {
 			glog.Fatalf("pemfile.NewProvider(%v) failed: %v", pemfileOptions, err)
 		}
-		httpS.TLSConfig = &tls.Config{GetCertificate: s3opt.GetCertificateWithUpdate}
+
+		caCertPool := x509.NewCertPool()
+		if *s3Options.tlsCACertificate != "" {
+			// load CA certificate file and add it to list of client CAs
+			caCertFile, err := ioutil.ReadFile(*s3opt.tlsCACertificate)
+			if err != nil {
+				glog.Fatalf("error reading CA certificate: %v", err)
+			}
+			caCertPool.AppendCertsFromPEM(caCertFile)
+		}
+
+		clientAuth := tls.NoClientCert
+		if *s3Options.tlsVerifyClientCert {
+			clientAuth = tls.RequireAndVerifyClientCert
+		}
+
+		httpS.TLSConfig = &tls.Config{
+			GetCertificate: s3opt.GetCertificateWithUpdate,
+			ClientAuth:     clientAuth,
+			ClientCAs:      caCertPool,
+		}
 		if *s3opt.portHttps == 0 {
 			glog.V(0).Infof("Start Seaweed S3 API Server %s at https port %d", util.Version(), *s3opt.port)
 			if s3ApiLocalListener != nil {
diff --git a/weed/command/server.go b/weed/command/server.go
index 7fbb59676..67e37426e 100644
--- a/weed/command/server.go
+++ b/weed/command/server.go
@@ -144,6 +144,8 @@ func init() {
 	s3Options.domainName = cmdServer.Flag.String("s3.domainName", "", "suffix of the host name in comma separated list, {bucket}.{domainName}")
 	s3Options.tlsPrivateKey = cmdServer.Flag.String("s3.key.file", "", "path to the TLS private key file")
 	s3Options.tlsCertificate = cmdServer.Flag.String("s3.cert.file", "", "path to the TLS certificate file")
+	s3Options.tlsCACertificate = cmdServer.Flag.String("s3.cacert.file", "", "path to the TLS CA certificate file")
+	s3Options.tlsVerifyClientCert = cmdServer.Flag.Bool("s3.tlsVerifyClientCert", false, "whether to verify the client's certificate")
 	s3Options.config = cmdServer.Flag.String("s3.config", "", "path to the config file")
 	s3Options.auditLogConfig = cmdServer.Flag.String("s3.auditLogConfig", "", "path to the audit log config file")
 	s3Options.allowEmptyFolder = cmdServer.Flag.Bool("s3.allowEmptyFolder", true, "allow empty folders")