Participation in aftercare may reduce risk of recidivism among women offenders with substance use problems following their release to the community. This study examines motivation to participate in aftercare among women offenders and whether their participation in both in-custody and aftercare treatment reduces their risk of recidivism. Surveys were conducted with women (N = 1,158) in prison-based substance abuse treatment programs. Return-to-prison was examined among participants in community-based aftercare (N = 1,182) over 12 months following treatment discharge. Higher treatment motivation was associated with child welfare involvement, prior treatment, and use of "harder" drugs; ethnic minority women had lower treatment motivation compared with White women. Participants who completed the aftercare program, or who had longer treatment duration, and those who had participated in an in-prison program prior to parole had reduced risk of recidivism. Study findings suggest the value of community aftercare for women offenders, particularly when combined with prior in-prison treatment.