A high-power thulium (Tm)-doped fiber chirped-pulse amplification system emitting a record compressed average output power of 152~W and 4~MW peak power is demonstrated. This result is enabled by utilizing Tm-doped photonic crystal fibers with mode-field diameters of 35~μm, which mitigate detrimental nonlinearities, exhibit slope efficiencies of more than 50\%, and allow for reaching a pump-power-limited average output power of 241~W. The high-compression efficiency has been achieved by using multilayer dielectric gratings with diffraction efficiencies higher than 98\%.