The quantitative determination of the three-dimensional Wulff shape for a metallic crystal-melt system is reported here. The anisotropy of crystal-melt interfacial free energy is experimentally measured for the Al–Sn binary system at temperatures of 300 and 500°C. Equilibrium shapes of liquid droplets entrained within the crystalline phase are measured experimentally on sequential two-dimensional sections, and the three-dimensional Wulff plot is reconstructed. For this system, it is found that a single-parameter description of anisotropy is not sufficient, and the anisotropy is reported using the leading terms of the relevant cubic harmonics. Accordingly, the anisotropy coefficients are determined to be ε1=(1.81±0.36)×10−2 and ε2=(−1.12±0.13)×10−2. In addition, the corresponding normal stiffness components as well as a generalized stiffness are quantified and compared with available predictions from atomistic simulations.