Although the molecular mechanisms of sex differentiation and gonad development are conserved across vertebrates, the most upstream sex-determining genes are quite different for different groups, especially for fish, whose sex-determining genes show obvious diversity. There are two types of sex determination in vertebrates, i.e. environmental sex determination and genetic sex determination. Environmental sex determination is mainly affected by temperature, light, hormones and pH, while genetic sex determination is generally determined by sex-determining gene located on sex chromosome. Transforming growth factor-β (TGF-β) signaling pathway is involved in a variety of biological processes. In recent years, many studies have shown that multiple sex-determining genes are members of the TGF-β signaling pathway, and this signaling pathway also plays an important role in sex differentiation of fishes. This paper summarizes the sex-determining genes or candidate genes that have been discovered and reported in fishes, and reviews in detail the role of TGF-β signaling pathway involved in sex determination and differentiation in fishes. We also discussed the mechanism of TGF-β signaling pathway involved in sex determination, which is important in understanding the role of TGF-β signaling pathway in fish sex determination, differentiation and sex control.