Background: Offering physical activity clubs (PACs) for students in urban high schools can provide avenues for increased physical activity (PA); however, little is known about why some clubs are not successful. Purpose: The purpose of this qualitative study was to examine leaders' and students' perspectives on the challenges faced when implementing PACs. Methods: Field observations (n = 115) and interviews with students (n = 278) and adult leaders (n = 126) were conducted over 2 years. The population-based health promotion model (PHPM) was used to analyze and interpret complex interrelationships. Results: Four themes emerged: (1) finding consistently available facility space, (2) providing snacks for adolescents, (3) securing reliable transportation, and (4) balancing clubs with other after-school obligations. Discussion: Leader and students reported challenges that intersected at all 3 streams: upstream, midstream, and downstream. With economic poverty within the community presenting as an upstream challenge, the importance of identifying midstream mechanisms becomes paramount, especially in the case of providing after-school nourishment for hungry students. With respect to transportation, upstream (e.g., community poverty; public transportation; environment) and midstream (e.g., school policies) influences converged and presented a barrier to PAC participation. Translation to Health Education Practice: Efforts to implement PACs should consider upstream parameters that imprint midstream school-level support.