A xenon flashlamp-pumped Cr∶Tm∶Ho∶YAG laser operating at 2.1 μm is demonstrated. Since the Cr∶Tm∶Ho∶YAG has a high threshold owing to its quasi-three-level nature and the complex energy transfer process between the doped ions, optimum ions concentration proportion and long pulse pumping are employed to achieve the 2.1-μm laser operating at room temperature. The ceramic pumping cavity with high diffuse reflectivity of 95% for effective pump band is used. With the cooling water temperature of 15 ℃, the maximum laser average power is 23.5 W at 10-Hz repetition frequency, and the maximum laser pulse energy is 2.58 J with a maximum slope efficiency of 4.3% at 5 Hz.