All-fiber mid-infrared supercontinuum source is obtained using ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) single-mode fiber, which has low transmission loss in this wavelength region. The supercontinuum is extended to mid-infrared wavelength. This scheme is based on multi-stage supercontinum generation in master oscillator power amplifier with nanosecond pulsed semiconductor seed laser operating at 1550 nm. The spectrum of seed laser is extended to 2.6 μm in Tm/Ho co-doped fiber, and the wavelength components lying in the gain band of Tm doped fiber are amplified in Tm doped double-clad fiber amplifier and then pump 10-m ZBLAN single-mode fiber. Spectral broadening from 1.9 μm to 4.3 μm with average output power of 185 mW is achieved resulting from the interaction between dispersion and nonlinear effects.