Metallothioneins (MTs) are a group of intracellular proteins of low molecular weight and rich cysteine, encoded by a family of genes containing at least 10 functional isoforms in human. MTs widely exist in the male reproductive system and are involved in many pathophysiological processes such as metal ion homeostasis and detoxification, protection against oxidative damage, cell proliferation and apoptosis, chemoresistance and radiotherapy resistance. This review describes the location and effects of MTs in the male reproductive system.