A method of estimating a torque of a transmission clutch may include adjusting an error, deducing an estimated engine angular speed and deducing an estimated clutch torque. The error may be adjusted by deducing an engine transient torque based on an engine angular speed measured using a sensor, an engine static torque deduced using a data map and a load torque depending on a driving load. The estimated engine angular speed may be deduced based on the engine static torque and the engine transient torque. The estimated clutch torque may be deduced by summing an integration value and an error compensation value. The integration value and the error compensation value may be deduced based on a difference between the estimated engine angular speed and the measured engine angular speed.