Gradle sync failed: 'com.android.build.gradle.BasePlugin' does not implement the Plugin interface

Faced the same issue after upgrading to android studio 2.1 from 1.5

Managed to resolve by updating the dependencies version if the gradle.gradleVersion >= 2.1 in the build.gradle file under buildscript {}

OLD Configuration

 if (gradle.gradleVersion >= "2.2") {    dependencies {        classpath 'com.android.tools.build:gradle:1.5.0'    }} else if (gradle.gradleVersion >= "2.1") {    dependencies {        classpath 'com.android.tools.build:gradle:0.14.0+'    }} else {    dependencies {        classpath 'com.android.tools.build:gradle:0.12.0+'    }}

Updated Configuration

if (gradle.gradleVersion >= "2.2") {    dependencies {        classpath 'com.android.tools.build:gradle:1.5.0'    }} else if (gradle.gradleVersion >= "2.1") {    dependencies {        classpath 'com.android.tools.build:gradle:2.1.0'    }} else {    dependencies {        classpath 'com.android.tools.build:gradle:0.12.0+'    }}

If you do not have if/else clause in your build.gradle you can update the dependencies directly as below,

dependencies {    classpath 'com.android.tools.build:gradle:2.1.0'}