A high power and high efficiency mid-infrared at 2.8 μm single mode fiber laser is demonstrated. Output power of exceeding 9 W from heavily Er3 +-doped ZBLAN double-clad fiber pumped by a laser-diode (LD) centered at 975 nm is obtained in continuous wave regime. The experimental results indicate that the maximum output power of the fiber laser is 9.2 W corresponding to the slope efficiency of 24.8%. Moreover, the threshold and the center wavelength are around 1.0 W and 2.79 μm, respectively. The fiber laser is in single mode operation, with beam quality factor M2 of less than 1.2.