We report, to the best of our knowledge, the first demonstration of a gain-switched fiber laser operating near 3.5 μm. A dual-wavelength pumping scheme consisting of a 1976 nm Q-switched fiber system and a continuous-wave 976 nm laser diode were used to gain-switch a monolithic erbium-doped fluorozirconate fiber laser cavity at 3.552 μm. Stable pulses were produced for repetition rates ranging between 15 and 20 kHz, and a record peak power of 204 W was achieved at 15 kHz. A quenching phenomenon was also observed at 15 kHz for 1976 nm pulse energies beyond 180 μJ.