We have systematically investigated the electronic structures and magnetic properties of nonmetal doped MoSe2 monolayer by using spin-polarized density functional theory calculations. Formation energies reveal that all doped systems are thermodynamically preferred under Mo-rich conditions than Se-rich conditions, and the incorporation of O atom into MoSe2 monolayer is most favorable. Electronic structure analysis elucidates that Cl, Br and I doped systems exhibit half-metallic properties, while the band gap has been significantly tuned by H, B, C, N, and F doping. More importantly, H, B, N, F, Cl, Br, and I doping can induce pronounced magnetic moments in host MoSe2 monolayer. (C) 2017 Elsevier B.V. All rights reserved.