The reaction mechanism of the N atom interaction with a single-layer MoS2, two-dimensional transition metal dichalcogenide, is considered in detail. These mechanisms were studied by DFT (density functional theory) modeling using both static and dynamic approaches. The most important processes for pristine and modified MoS2surfaces are revealed. For incident N atoms both the scattering and recombination with adsorbed atoms are prevailed. Various formation mechanisms for vacancies and other defects by thermal and hot N atoms are proposed and discussed. The results of dynamic DFT simulations are used to illustrate the reaction pathways.