Mammalian gametogenesis relies on a complex program of mitotic, meiotic and differentiation processes that are strictly regulated by stage- and germ-cell specific gene expression. Tob1 is a member of the BTG/TOB family of proteins with established roles as negative regulators of cell proliferation. In mouse and human Tob1 is expressed in multiple adult tissues including the testis and ovary but the specific cell types that express Tob1 in gonads was unknown. In this study we examined murine Tob1 gene expression by droplet digital PCR in developing germ cells and sorted male germ cells (gonocytes, spermatogonia, pachytene spermatocytes and round spermatids), and in situ hybridization in adult ovary and testis. Tob1 protein expression in adult ovary and testis was done by immunofluorescence. Tob1 expression was uniformly low in developing male germ cells but increased 10-fold in developing female germ cells undergoing entry into meiosis (E15.5) compared to E12.5 germ cells. In adult testis Tob1 mRNA was most highly expressed in round spermatids. Round spermatids and oocyte in all stages of folliculogenesis were positive for Tob1 protein. Notably, a marker for P-bodies, Dcp-2, was also highly expressed in round spermatids and in all oocyte stages examined. The cytoplasmic presence of the Tob1 protein in round spermatids and oocytes, and its association withDcp2 in both cell types, suggests Tob1 protein may play a role in post-transcriptional mechanisms during gametogenesis.