A solvent-controlled selective synthesis of amides and thioureas from isothiocyanates in the presence of base is described. Amides were obtained via the base-promoted reaction of isothiocyanates and nitrile solvent. Interestingly, the use of water instead of a nitrile solvent provided symmetrical and unsymmetrical disubstituted thioureas. This protocol exhibits excellent chemoselectivity and practicality.