Block of proliferation 1 (BOP1) is a nucleolar protein that affects the protein synthesis by its participation in ribosome biogenesis. Recent investigations suggest that BOP1 overexpression occurs in some tumors, which plays a critical role in epithelial-to-mesenchymal transition (EMT), and cancer occurrence and development as well as invasion and metastasis. The mechanism of BOP1 function in cancer remains unclear. This paper reviews the recent understanding of the biological characteristics of BOP1 and its relation with cancer.