In this Letter, a high-power diode-side-pumped Nd:YAG laser emitting at 1338 nm is described. The output characteristics of the laser using the different output couplers for both the cw mode and the Q-switched mode have been studied. With a pumping power of 555 W, the average output power decreases from 70 W at 50 kHz to 55 W (slope efficiency 21.2%, optical conversion efficiency 10%) at 5 kHz. The highest peak power is up to 73 kW with the pulse duration of 150 ns at the repetition rate of 5 kHz. When operated in cw mode, the output power of 100.5 W was achieved, corresponding with the optical slope efficiency of 36%.