Flowerlike nanospheres of ZnIn2S4 consisting of interweaving nanoflakes were prepared by a rapid microwave-assisted solvothermal method. The photocatalytic performance of ZnIn2S4 in the aerobic oxidation of amines to imines is for the first time revealed. As-prepared ZnIn2S4 showed high efficiency for the transformations of various amines into their corresponding imines under visible-light irradiation by using air as the oxidant. The photocatalytic performance of ZnIn2S4 in the selective oxidation of amines to their corresponding imines is much higher than that of graphitic C3N4 and CdS previously reported. A plausible mechanism involving the oxygenation of amines to form aldehydes, followed by the nucleophilic addition of the amines to afford the final imines is proposed. The use of a cheap, environmentally friendly inorganic semiconductor photocatalyst and solar energy makes this transformation green and sustainable.