Sectarianism is perceived as a serious issue in Scotland despite a lack of concrete evidence, according to the Advisory Group on Tackling Sectarianism. This paper addresses one of the gaps in knowledge, the attitudes of Catholic school pupils. Our research was designed to profile sectarian attitudes among a sample of Catholic school pupils in Scotland, using our own newly designed "Scale of Catholic Sectarian Attitudes." The research assessed the influence of five sets of factors on shaping individual differences in sectarian attitudes: personal factors (sex and age), psychological factors (personality), religious factors (identity, belief, and practice), theological factors (exclusivism), and contextual factors (Catholic schools). The study draws on data provided by 797 13- to 15-year-old school pupils from schools in Scotland who self-identified as Roman Catholic. We offer a new tool for measuring attitudes to sectarianism and also findings that demonstrate that sectarian attitudes exist within the young Catholic community in Scotland and that this has possibly become part of a wider problem generated by the public visibility of religious diversity within an increasingly secular society. Further we find that Sectarian attitudes are higher among males than among females and are higher among nominal Catholics than among practising Catholics.