This study findings suggest that a behavior change intervention helped overweight men living in less walkable neighborhoods to overcome environmental barriers to walking. Those in more walkable neighborhoods, with higher baseline walking levels, did not increase their walking, suggesting a possible ceiling effect. Among overweight women, regardless of intervention condition, those with high levels of perceived traffic safety were more likely to increase their walking over one year. Present results support the need to develop and evaluate multi-level physical activity interventions that target changes in individuals, social environments, and built environments, but men and women may respond differently to specific components.