Medication nonadherence is one of the most important reasons for treatment failure in patients with epilepsy. The present study investigated the effectiveness of a multicomponent intervention to improve adherence to antiepileptic drug (AED) medication in patients with epilepsy. In a prospective, randomized multicenter trial, three sessions of face-to-face motivational interviewing (MI) in combination with complementary behavior change techniques were compared with standard care. Motivational interviewing prompted change talk and self-motivated statements from the patients, planning their own medication intake regimen and also identifying and overcoming barriers that may prevent adherence. Participants were provided with calendars to self-monitor their medication taking behavior. A family member and the health-care team were invited to attend the last session of MI in order to improve the collaboration and communication between patients, their caregiver or family member, and their health-care provider. At baseline and 6-month follow-up, psychosocial variables and medical adherence were assessed. In total, 275 participants were included in the study. Compared with the active control group, patients in the intervention group reported significantly higher medication adherence, as well as stronger intention and perceptions of control for taking medication regularly. The intervention group also reported higher levels of action planning, coping planning, self-monitoring, and lower medication concerns. This study shows that MI can be effective in clinical practice to improve medication adherence in patients with epilepsy. It also provides evidence that combining volitional interventions, including action planning, coping planning, and self-monitoring with motivational interviewing can promote the effectiveness of the medical treatments for epilepsy by improving adherence.