Brand evangelism, an advanced form of marketing where consumers voluntarily advocate on behalf of the brand, can bring numerous benefits to a firm. Pro-brand behaviors such as word-of-mouth promotion, recruitment of consumers, and disparagement of rivals are just a few of the many actions associated with brand evangelism. With highly impassioned and provocative fans, an opportunity exists to explore brand evangelism within the spectator sport context. The purpose of this study was to develop and validate a scale to measure sport team (brand) evangelism. Guided by Fournier’s (1998) brand extension of relationship theory and following Churchill’s (1979) eight-step method for developing marketing measures, two focus groups of fans were interviewed and an additional 450 sport fans were surveyed through two distinct data collections in an attempt to identify sport team evangelistic behaviors, and test a measure of such behaviors. The assessment of the instrument included two forms of reliability analysis and three modes of validity analysis as the scale was parsimoniously reduced from 88 initial behaviors to four factors and 14 items.