The electronic band structures of orthorhombic (oP28) and monoclinic (mC28) MnSb2S4 were investigated with ab initio calculations in the local spin density approximation to the density functional theory. An analysis of the electronic properties and of the chemical bonding is provided using the augmented spherical wave method considering nonmagnetic, ferromagnetic, ferrimagnetic, and antiferromagnetic model orderings. In agreement with experimental results both modifications of MnSb2S4 are predicted to be antiferromagnetic. While the experimental band gap is missed for the monoclinic polymorph, the calculated band gap for orthorhombic MnSb2S4 is close to the experimental one.