Density functional theory computations were carried out to examine the effects of doping 4d transition metals (Mo, Nb, Rh and Ru) on the structural and electronic properties of stanene monolayers. Our results suggested that Mo-doped stanene nanosheet exhibited metallic behavior, while the Nb, Rh and Ru-doped ones revealed semiconducting character. The metallic behavior of the Mo-doped stanene is mainly attributed to the emergence of electronic band across the Fermi level. Our formation energy calculations also showed that all considered 4d transition metal doped stanene nanosheets are energetically stable. The lowest formation energy and highest stability belongs to Ru-doped stanene system. The electron density difference graphs of the transition metal doped systems also showed the accumulation of charge density over the interaction sites between metal adatoms and neighboring tin atoms. Thus, all the studied transition metals strongly coordinated to the tin atoms, as confirmed by the projected density of states graphs. Our results could help to understand the influence of 4d transition metals in 2D buckled stanene nanosheets.