The 2-μm spectral window is emerging as a promising candidate for the next generation communication. We present a 2 × 2 Mach-Zehnder interferometric thermo-optic switch at 2-μm waveband. The device is fabricated on a 220 nm thick silicon-on-insulator wafer with standard complementary metal oxide semiconductor (CMOS) process. We demonstrate an over 30 dB extinction ratio under the power consumption of 32.3 mW, with an average switching time of ~15 μs. This proof of principle optical switch paves a way toward full silicon-based chip-scale interconnects in the 2-μm waveband.