Ensuring treatment adherence is critical for the success of antiretroviral therapy (ART) programs in developing countries. Enlisting NGOs or persons living with HIV/AIDS (PLHA) group members as treatment supporters is one common strategy. Less attention is given to family members and especially older-age parents. Yet ART patients often live with other family members who are highly motivated to ensure treatment success. This study examines the role of family members and especially parents in assisting adherence in Cambodia and Thailand among adult ART patients. Most have a living parent and many live with or near a parent. Family members including parents commonly remind patients to take medications, particularly if coresident in the same household. Parents also remind patients to get resupplies and accompany them to appointments. Some contrasts between Cambodia and Thailand emerged. Fewer Cambodian than Thai patients had a living parent. However, among those who did, equal shares lived with parents. Cambodian parents more commonly reminded patients to take medications and get resupplies and accompanied them when doing so. In both countries correct knowledge of ART among parents was associated with the amount of advice from program personnel. The results underscore both the need to more explicitly incorporate close family members, including parents, into efforts to promote adherence and need for PLHA peers and home based care teams to provide them with adequate information, training and resources to increase their effectiveness.