Ab initio molecular orbital calculations have been carried out for the N(D-2) + H2O reaction. The reaction pathways were examined at the PMP4(full,SDTQ)/cc-pVTZ//MP2(full)/cc-pVTZ level of theory. It was calculated that the most stable intermediate product is H2NO(B-2(1)) and the main product channels are NH((3)Sigma) + OH((2)Pi), HNO((1)A') + H, and NO((2)Pi) + H-2. It was found that a nonadiabatic process significantly contributes to the NO((2)Pi) + H-2 channel. The contour plots of the potential surface were obtained at the FOCI/cc-pVTZ level in order to understand initial steps of the N(D-2) + H2O reaction: the N insertion into the OH bond, the N addition to the O atom, and the H atom abstraction by N. It was predicted that the N addition is the most favorable reaction pathway among these initial steps.