The aim of our work is to discover molecular biology mechanisms underlying testis regression in mink. To this end, HE staining technique was used to examine the histological morphology of mink testis at different stages during regression. In addition, real-time PCR (RT-PCR) was applied to determining the expression levels of the members of transforming growth factor beta (TGFB) family and their receptors at different stages in mink testes. Our results showed that the diameters and the weights of the mink testis were gradually reduced after April, being only half of the diameter and 1/8 of the weight in July. In parallel, histological assessment demonstrated that mink testis experienced severe regression, i.e. the lumen of the seminiferous tubules was progressively absent, while the diameter of the seminiferous tubules was reduced to 1/3 of its largest size during the same time. The RT- PCR data indicated that the expression levels of the members of TGFB, such as TGFb3, INHBA; and their receptors, like TGFBR1, ACVR2A, ACVR2B, SMAD2 and SMAD4, decreased in the mink testis from April to July. Our study suggests that the signaling pathways of the TGFB superfamily may play a key role in preventing degeneration in the mink.