diff --git a/plugin/pkg/auth/authenticator/password/passwordfile/BUILD b/plugin/pkg/auth/authenticator/password/passwordfile/BUILD
index bdb1faa618f..81a9dfe29dd 100644
--- a/plugin/pkg/auth/authenticator/password/passwordfile/BUILD
+++ b/plugin/pkg/auth/authenticator/password/passwordfile/BUILD
@@ -14,7 +14,10 @@ go_library(
     name = "go_default_library",
     srcs = ["passwordfile.go"],
     tags = ["automanaged"],
-    deps = ["//pkg/auth/user:go_default_library"],
+    deps = [
+        "//pkg/auth/user:go_default_library",
+        "//vendor:github.com/golang/glog",
+    ],
 )
 
 go_test(
diff --git a/plugin/pkg/auth/authenticator/password/passwordfile/passwordfile.go b/plugin/pkg/auth/authenticator/password/passwordfile/passwordfile.go
index 2042416840c..6496143223a 100644
--- a/plugin/pkg/auth/authenticator/password/passwordfile/passwordfile.go
+++ b/plugin/pkg/auth/authenticator/password/passwordfile/passwordfile.go
@@ -22,6 +22,7 @@ import (
 	"io"
 	"os"
 
+	"github.com/golang/glog"
 	"k8s.io/kubernetes/pkg/auth/user"
 )
 
@@ -43,6 +44,7 @@ func NewCSV(path string) (*PasswordAuthenticator, error) {
 	}
 	defer file.Close()
 
+	recordNum := 0
 	users := make(map[string]*userPasswordInfo)
 	reader := csv.NewReader(file)
 	for {
@@ -60,6 +62,10 @@ func NewCSV(path string) (*PasswordAuthenticator, error) {
 			info:     &user.DefaultInfo{Name: record[1], UID: record[2]},
 			password: record[0],
 		}
+		recordNum++
+		if _, exist := users[obj.info.Name]; exist {
+			glog.Warningf("duplicate username '%s' has been found in password file '%s', record number '%d'", obj.info.Name, path, recordNum)
+		}
 		users[obj.info.Name] = obj
 	}
 
diff --git a/plugin/pkg/auth/authenticator/token/tokenfile/BUILD b/plugin/pkg/auth/authenticator/token/tokenfile/BUILD
index 593e3f09559..55efbf196f4 100644
--- a/plugin/pkg/auth/authenticator/token/tokenfile/BUILD
+++ b/plugin/pkg/auth/authenticator/token/tokenfile/BUILD
@@ -14,7 +14,10 @@ go_library(
     name = "go_default_library",
     srcs = ["tokenfile.go"],
     tags = ["automanaged"],
-    deps = ["//pkg/auth/user:go_default_library"],
+    deps = [
+        "//pkg/auth/user:go_default_library",
+        "//vendor:github.com/golang/glog",
+    ],
 )
 
 go_test(
diff --git a/plugin/pkg/auth/authenticator/token/tokenfile/tokenfile.go b/plugin/pkg/auth/authenticator/token/tokenfile/tokenfile.go
index b0942340d7a..b973556f8da 100644
--- a/plugin/pkg/auth/authenticator/token/tokenfile/tokenfile.go
+++ b/plugin/pkg/auth/authenticator/token/tokenfile/tokenfile.go
@@ -23,6 +23,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/golang/glog"
 	"k8s.io/kubernetes/pkg/auth/user"
 )
 
@@ -46,6 +47,7 @@ func NewCSV(path string) (*TokenAuthenticator, error) {
 	}
 	defer file.Close()
 
+	recordNum := 0
 	tokens := make(map[string]*user.DefaultInfo)
 	reader := csv.NewReader(file)
 	reader.FieldsPerRecord = -1
@@ -64,6 +66,10 @@ func NewCSV(path string) (*TokenAuthenticator, error) {
 			Name: record[1],
 			UID:  record[2],
 		}
+		recordNum++
+		if _, exist := tokens[record[0]]; exist {
+			glog.Warningf("duplicate token has been found in token file '%s', record number '%d'", path, recordNum)
+		}
 		tokens[record[0]] = obj
 
 		if len(record) >= 4 {