Samarium nickelate ($\mathrm{Sm}\mathrm{Ni}{\mathrm{O}}_{3}$) is a representative quantum material, presenting ``exotic'' properties including strong correlations and metal-to-insulator transition. It was also shown that $\mathrm{Sm}\mathrm{Ni}{\mathrm{O}}_{3}$ presents the unusual antidoping effect, where the resistivity of the material increases with doping instead of decreasing. In this paper, we study intrinsic defects in this compound, and discuss the antidoping behavior in the presence of these defects. Our results show that the negatively charged oxygen vacancy (${V}_{\text{O}}^{\ensuremath{-}2}$) can be very stable, and the extra electrons move towards the small octahedra (${\mathrm{Ni}}^{4+}$ sites), similar to the antidoping effect in the pristine material. This indicates that antidoping should still be observed even in the presence of defects.