Poor social support is a contributory factor in development of addictive disorders, but it has rarely been evaluated in pathological gamblers. This study examined social support in pathological gamblers and its relationship with treatment outcomes. Low baseline social support was associated with increased severity of gambling, family, and psychiatric problems and poorer post-treatment outcomes. Further, social support assessed post-treatment was significantly related to severity of gambling problems at the 12-month follow-up. These findings demonstrate that social support plays an important role in moderating outcomes, and enhancing social support may be an important aspect of effective gambling treatments.