We performed combined theoretical and experimental studies of electronic, structural, and magnetic properties of Fe2MnSn Heusler alloy. The density functional theory calculation shows that the Fe2MnSn alloy has two energetically close phases, namely, hexagonal D019 and cubic L21, which agrees well with the experimental results. Both the hexagonal and cubic phases are ferromagnetic, with large magnetization values of about 6 μB/f.u. and high Curie temperature above room temperature. The hexagonal phase shows high magnetic anisotropy of 5.1 Merg/cm3. These findings may be interesting for magnetic applications where large saturation magnetization, high Curie temperature, and high magnetic anisotropy are desired.