We report a 2800 nm Er3+-doped fluoride fiber amplifier that delivers 1 mJ pulses with an average power of 5 W and pulse duration of 1 ns at 5 kHz repetition rate. To the best of our knowledge, this is the highest pulse energy achieved from a fluoride-fiber-based system operating near 3 µm, and the W-level average power and short pulse lengths make the system a promising tool for biomaterials processing.