A major aim of the current study was to determine what classroom teachers perceived to be the greatest barriers affecting their capacity to deliver successful physical education (PE) programs. An additional aim was to examine the impact of these barriers on the type and quality of PE programs delivered. This study applied a mixed-mode design involving data source triangulation using semistructured interviews with classroom teachers (n = 31) and teacher-completed questionnaires (n = 189) from a random sample of 38 schools. Results identified the key factors inhibiting PE teachers, which were categorized as teacher-related or institutional. Interestingly, the five greatest barriers were defined as institutional or out of the teacher's control. The major adverse effects of these barriers were evident in reduced time spent teaching PE and delivering PE lessons of questionable quality. (Contains 1 table and 1 figure.)