Manganese sulfide (MnS) crystallites with varying morphology and polymorph can be synthesized via a solvothermal process assisted by mineralizers. It was found that KOH or KNO3 as a mineralizer played a key role in the crystallization and development of different kinds of MnS crystallites. Adding KOH in the solvothermal process resulted in the formation of alpha-MnS crystallites, but gamma-MnS could be produced by introducing KNO3 as a mineralizer. The morphology control was also available.