An apparatus and method for accurately estimating the transfer torque of an engine clutch provided between an engine and a motor in a hybrid electric vehicle, may include a forward estimation device configured for determining a first estimate of engine clutch transfer torque using engine torque information, a reverse estimation device configured for determining a second estimate of the engine clutch transfer torque using a drive system model including wheels, a transmission, and a motor and using wheel speed information, a weight determination device configured for determining a weight based on brake input by a driver and whether predetermined devices in the vehicle are operated, and an estimate combination determination device configured for determining a final estimate of the engine clutch transfer torque as a value combined by applying a weight to the determined first estimate and the determined second estimate.