Searching for experimentally feasible intrinsic two-dimensional ferromagnetic semiconductors is of great significance for applications of nanoscale spintronic devices. Here, based on the first-principles calculations, an Ni(NCS)2 monolayer was systematically investigated. The results showed that the Ni(NCS)2 monolayer was a robust bipolar ferromagnetic semiconductor with a moderate bandgap of ∼1.5 eV. Based on the Monte Carlo simulation, its Curie temperature was about 37 K. Interestingly, the Ni(NCS)2 monolayer remains ferromagnetic ordering when strain and electron doping were applied. However, ferromagnetic-to-antiferromagnetic phase transition occurred when high concentrations of holes were doped. Besides, the Ni(NCS)2 monolayer is confirmed to be potentially exfoliated from its bulk forms due to its small exfoliated energy. Finally, the Ni(NCS)2 monolayer's thermodynamic, dynamic, and mechanical stabilities were confirmed by the phonon spectrum calculation, ab initio molecular dynamics simulation and elastic constants calculation, respectively. The results showed that the Ni(NCS)2 monolayer, as a novel 2D ferromagnetic candidate material of new magnetic molecular framework materials, may have a promising potential for magnetic nanoelectronic devices.