Understanding the magnetic properties of the various Mn doping configurations that can be encountered in 2H-MoS2 monolayer could be beneficial for its use in spintronics. Using density functional theory plus Hubbard term (DFT + U) approach, we study how a single isolated, double- and triple-substitution configurations of Mn atoms within a MoS2 monolayer could contribute to its total magnetization. We find that the doping-configuration plays a critical role in stabilizing a ferromagnetic state in a Mn-doped MoS2 monolayer. Indeed, the Mn-Mn magnetic interaction is found to be ferromagnetic and strong for Mn in equidistant substitution positions where the separation average range of 6-11 [Formula: see text]. The strongest ferromagnetic interaction is found when substitutions are in second nearest neighbor Mo-sites of the armchair chain. Clustering is energetically favorable but it strongly reduces the ferromagnetic exchange energies. Furthermore, in term of electronic properties, we show that the Mn-doped MoS2 monolayer can change its electronic behavior from semiconductor to half-metallic depending on the doping configuration. Our results suggest that ordering the Mn dopants on MoS2 monolayer is needed to increase its potential ferromagnetism.