A method and an apparatus for controlling an engine clutch are provided. The method includes determining whether an engine start condition is satisfied when an engine is stopped and performing an engine cranking operation by operating a hybrid starter & generator (HSG) when the engine start condition is satisfied. Whether an engine speed is greater than or equal to a first reference speed is determined to thus reduce an HSG torque. Then, whether the engine speed is greater than or equal to a second reference speed is determined to thus calculate a target speed of the engine. A speed control of the engine is performed using the target speed of the engine while determining whether an engine clutch engagement condition is satisfied. An engine clutch is engaged when the engine clutch engagement condition is satisfied.