This study analyzed whether family variables such as marital adjustment, partner support, family coping, and family stress moderated the relationship between negative beliefs about medicines and adherence to self-care behaviors (diet, glucose monitoring, exercise, foot care, and medication), in Type 2 diabetes patients. The sample was composed of 387 individuals with Type 2 diabetes, diagnosed in the past 12 months. Patients were assessed on self-care behaviors in diabetes, medication adherence, beliefs about medicines, family coping, family stress, marital adjustment, and partner support. The results showed marital adjustment, family coping, partner support, and family stress as moderators in the relationship between negative beliefs and adherence. Patients with negative beliefs regarding medicines, but who reported good marital adjustment and family coping were more likely to test their blood glucose; and if they reported low support from their partners were less likely to adhere to their prescribed diet. Finally, patients with negative beliefs about medicines, but who reported high family stress, were less likely to take their medication. The results emphasize the importance of family variables on adherence to self-care behaviors and medication. This study revealed the importance of including partners on interventions regarding Type 2 diabetes because they seem to play an important role in patient’s adherence.