The electronic, elastic, and optical properties of MnIn2S4 were investigated using first-principle calculations based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. The study revealed that MnIn2S4 has indirect allowed transitions for both DFT and DFT + U (U = 6 eV) with energy band gaps of 1.57 eV and 2.095 eV, respectively. The elastic constants and various optical properties of MnIn2S4 including the dielectric constant, absorption coefficient, electron energy loss function and reflectivity were calculated as a function of incident photon energy. Those results are discussed in this study and compared with available experimental results.