This paper examines the attitudes of Monsignor Francis Xavier Gsell MSC, superintendent of the Catholic mission to Bathurst Island, and his efforts to restrict so-called ‘illicit’ interactions between Japanese pearlers and Tiwi women. In 1928, Gsell complained to Commonwealth authorities that: ‘one evil seems to be increasing every year, and threatens the very existence of the native race, and that is the wholesale prostitution carried on by the crews of the pearling luggers’. The resulting national scandal and consequent government responses demonstrate the perceived threat to White Australia posed by mixed communities living in the country’s North. It also highlights the ways in which Gsell, the fabled ‘Bishop with 150 wives’, articulated and justified his rather unorthodox missionary methods.