This paper explores the relationship between direct support from family members and friends and substance use outcomes for people with co-occurring severe mental illness and substance use disorders. Data are from a 3-year randomized trial of 203 patients in treatment for dual disorders. Informal (family) caregivers for 174 participants were asked about economic assistance and direct care that they provided to participants. Associations between family support and substance use outcomes were examined with bivariate comparisons of abstainers and nonabstainers and with regression models using change in substance use and cumulative substance use as dependent measures. Family economic support was associated with substance abuse recovery in bivariate and regression analyses. Caregiving hours were significantly associated with substance use reduction but not with cumulative substance use. Informal support was not associated with changes in psychiatric symptoms. The findings suggest that direct family support may help people with dual disorders to reduce or eliminate their substance use. Further research is needed to confirm this connection and to establish the mechanisms by which support is useful.