Several native point defects in MoS2 are theoretically studied, using first-principles simulations. The isotropic g-values of these defects are computed, and compared to recently reported experimental results, obtained from electron spin resonance experiments performed on MoS2 layers synthesized by the sulfurization of Mo films. We tentatively assign the observed electron spin resonance signal with isotropic g-value of 2.002 to a sulfur antisite defect. This defect presents energy levels in the MoS2 band-gap, and could hamper the proper functioning of MoS2-based field effect transistors. We next study the interaction of H-2 molecules with the sulfur antisite defect, using first-principles molecular dynamics simulations and the nudged elastic band method. Our results predict that this defect can be passivated by hydrogen, with a computed activation energy of about 1.5 eV. (C) 2017 Elsevier B.V. All rights reserved.