Human services occupations are prone to high rates of burnout and turnover. These outcomes have adverse implications for service providers and the clients in their care. Several studies have assessed the structural causes and consequences of burnout and turnover, but little attention has been paid to the potentially protective role of coworker support. We estimate a structural equation model including job characteristics, coworker support, and workplace justice to predict turnover intention, both directly and indirectly through emotional exhaustion. More than 1,800 substance abuse treatment counselors provided survey data for these analyses. Net of demographic and workload measures, low autonomy, and a lack of distributive justice significantly predicted emotional exhaustion, while coworker support was inversely associated with exhaustion. In turn, exhaustion was a significant predictor of intent to quit. Coworker support exhibited direct inverse effects on intent to quit, while counselors reporting low autonomy and lack of workplace justice were more likely to be contemplating quitting. These findings extend previous research by identifying specific and beneficial effects of coworker support on counselors' job-related affect and well-being.