A method of operating a drive train of a motor vehicle with a hybrid drive having an internal combustion engine, an electric motor, an automatic transmission. The drive train also having a clutch between the internal combustion engine and the electric motor, and a clutch or a torque converter between the electric motor and the automatic transmission. This arrangement enabling the internal combustion engine to be started by engaging the clutch arranged between the internal combustion engine and the electric motor, when the drive train is powered exclusively by the electric motor. The braking power, generated during an upshift in response to a drop in the rotational speed of the drive train components, is used to start the internal combustion engine, such that the energy required from the electric motor for starting the combustion engine is minimized.