A power transmission system for a hybrid vehicle according to an exemplary embodiment of includes an input shaft through which torque from an engine, which is a power source, is inputted, first and second motor/generators that have the functions of both of a motor and a generator, as individual power sources, a planetary gear set that may be disposed on a line from the input shaft and includes a first rotating element directly connected with the first motor/generator and selectively connected to a transmission housing, a second rotating element directly connected with the input shaft and selectively connected to the transmission housing, and a third rotating element operating as an output element and connected with the second motor/generator, an output shaft that transmits torque from the planetary gear set and the second motor/generator to driving wheels through a differential, and a friction member disposed on the selective connecting portion.