Objectives: The purpose of the study was to examine potential differences between two approaches to defining adolescent weight misperception. Specifically, weight status perception was compared with self-reported weight status and actual weight status (based on body mass index percentiles calculated from self-reported and actual weights and heights, respectively). Furthermore, the accuracy of assigning weight status based on body mass index percentiles calculated from self-reported weights and heights was assessed by comparing them with actual weight status. Methods: Data were extracted from Team Up for Healthy Living, an 8-week, school-based obesity prevention program in southern Appalachia. Participants (N = 1509) were predominately white (93.4%) and ninth graders (89.5%), with approximately equivalent representation of both sexes (50.7% boys). Results: The study revealed significant differences between the approaches to defining weight misperception (χ2 = 16.2; P = 0.0003). Conclusions: Researchers should interpret study findings with awareness of potential differences based on the method of calculating weight misperception.