PURPOSE Get in Motion (GIM) is an evidence-based telephone counseling service that promotes leisure-time physical activity (LTPA) among Canadian adults with spinal cord injury (SCI). The first phase of GIM sustained intentions for, and increased participation in, LTPA; however, it is unclear how GIM led to these outcomes. The purpose of this study was to explore the implementation correlates of change in LTPA intentions and behavior in the second phase of GIM. METHODS The frequency, duration, and content of counseling sessions were tailored to meet clients' (N = 46; 50.0% male; 50.0% paraplegia; 51.46 (SD 12.36) years old) needs and preferences. Intervention dose and content were monitored using Counseling Session Checklists. Clients self-reported their intentions for and actual aerobic and strength-training LTPA participation at baseline, 2-, 4-, and 6-months, and their perceptions of service quality at 6-months. RESULTS The second phase of GIM effectively sustained LTPA intentions and increased time spent on moderate-to-vigorous strength-training and total LTPA. Increases in clients' moderate-to-vigorous aerobic LTPA were significantly positively related to intervention dose, intervention content (both informational and behavioral strategies), and clients' perceptions of service credibility. CONCLUSIONS This study identified intervention dose and content as key implementation variables for an LTPA telephone counseling service for adults with SCI. Implications for Rehabilitation An evidence- and theory-based telephone counseling service can effectively sustain LTPA intentions and increase LTPA behavior among adults with SCI. The first two months of the service are a critical period for enhancing LTPA participation and for minimizing dropouts. The provision of both informational and behavioral strategies is important for increasing aerobic LTPA levels among adults with SCI.