Single-frequency laser emission from a distributed feedback all-fiber laser operating in the vicinity of 3 μm is demonstrated. The laser cavity was made of a 30 mm long π-phase-shifted fiber Bragg grating inscribed in a heavily erbium-doped fluoride fiber using infrared femtosecond pulses and the dithering phase-mask technique. A maximum CW output power of 12 mW was obtained at 2794.4 nm by using a multimode pumping scheme. The narrow linewidth was characterized to be lower than 20 kHz using a heterodyne technique. This achievement represents a significant step toward the development of active frequency references operating in the mid-infrared.