Study design: Grounded theory qualitative approach. Objectives: To examine critical factors associated with interest in enrolling in a physical activity (PA) research intervention among a predominant group of adults with spinal cord injury (SCI) and develop a theory that can enhance future recruitment success. Setting: Participants were recruited through the network of a community exercise facility for people with physical disabilities. Methods: Interviews were conducted with 22 wheelchair users (mean age 46 ± 13 years; SCI [n = 19], cerebral palsy [n = 1]; multiple sclerosis [n = 1]; and bilateral limb loss [n = 1]) in either a one-on-one format or focus group. Interview data were coded, and these codes were organized into conceptual categories using a constructivist grounded theory framework. Results: Adults with SCI conceive three core concerns with enrolling into a PA trial: (1) capability to participate in the program due to scheduling, transportation, and secondary health conditions; (2) mental balancing of anticipated benefits versus the difficulty of starting the program; and (3) desirability of the program characteristics based on their preferences and needs. Concerns were organized into a theory that may enhance future recruitment success. Conclusions: Recruitment is often overlooked in PA research for people with SCI despite it being a primary rate-limiting factor that severely limits the external validity of published studies. Study findings identified core recruitment concerns that are likely similar with general barriers to PA participation. This paper proposed a 3-step decision-making process that can serve as a starting point for overcoming recruitment issues in PA research with people with SCI.