Background. Individuals with brain impairment (BI) are less active than the general population and have increased risk of chronic disease. Objective. This controlled trial evaluated the efficacy of a physical activity (PA) intervention for community-dwelling adults with BI. Methods. A total of 43 adults with BI (27 male, 16 female; age 38.1 ± 11.9 years; stage of change 1-3) who walked as their primary means of locomotion were allocated to an intervention (n = 23) or control (n = 20) condition. The intervention comprised 10 face-to-face home visits over 12 weeks, including a tailored combination of stage-matched behavior change activities, exercise prescription, community access facilitation, and relapse prevention strategies. The control group received 10 face-to-face visits over 12 weeks to promote sun safety, healthy sleep, and oral health. Primary outcomes were daily activity counts and minutes of moderate-to-vigorous-intensity PA (MVPA) measured with the ActiGraph GT1M at baseline (0 weeks), postintervention (12 weeks) and follow-up (24 weeks). Between-group differences were evaluated for statistical significance using repeated-measures ANOVA. Results. MVPA for the intervention group increased significantly from baseline to 12 weeks (20.8 ± 3.1 to 31.2 ± 3.1 min/d; P = .01), but differences between baseline and 24 weeks were nonsignificant (20.8 ± 3.1 to 25.3 ± 3.2 min/d; P = .28). MVPA changes for the control group were negligible and nonsignificant. Between-group differences for change in MVPA were significant at 12 weeks (P = .03) but not at 24 weeks (P = .49). Conclusion. The 12-week intervention effectively increased adoption of PA in a sample of community-dwelling adults with BI immediately after the intervention but not at follow-up. Future studies should explore strategies to foster maintenance of PA participation.