Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber. Until now, spatiotemporal mode-locking has only been realized in normal-dispersion dissipative soliton and similariton fiber lasers. In this paper, we demonstrated the first experimental realization of a spatiotemporally mode-locked soliton laser in mid-infrared fluoride fiber with anomalous dispersion. The mode-locked fluoride fiber oscillator directly generated a record pulse energy of 16.1 nJ and peak power of 74.6 kW at 2.8 μm wavelength. This work extends the spatiotemporal mode-locking to soliton fiber lasers and should have a wide interest for the laser community.