Background: Medication adherence, which is how much is the patient committed to their medications, is an important factor in improving clinical outcomes and reducing mortalities. This adherence issue should not be the responsibility of the patients and the doctors only but also the pharmacists have to take a role to guarantee that the patients stay adherent. Objectives: To determine whether the role of pharmacists and their provided services, which were delivered either directly to patients or indirectly by their responsible physicians, have a significant positive impact on medication adherence or not. Method: A systematic review was conducted containing Seventy-Four studies either related to interventions done by the pharmacists and their effects on medication adherence or studies about result of questionnaires and surveys that highlighted how much the pharmacist is an important element in health care system. The studies were taken from three databases PubMed, Web of Science and Science Direct. After that, a quality assessment tool was applied on the included articles to clarify if they were weak, moderate or strong. Results: Sixty-one studies were intervention studies where the pharmacists were responsible for many interventions like patient education, counseling, motivational interviewing, pharmacists’ participation in emergency department in the hospital or primary care clinics, home mediated review and others. Fifty studies resulted in positive effect of the intervention on medication adherence especially patient education and the counseling and eleven studies showed that there is no significant change after the intervention. Adherence was measured in many different validated tools like Morisky scale, Proportion of Days Covered (PDC), refill report and others. The remaining thirteen studies were interviews and surveys to patients and health care workers which highlighted the role of the pharmacists. After evaluating these studies on quality assessment tool, which was general tool since the type of studies and the methodology were different, the results were that only five studies were strong, thirty moderate and thirty-nine weak. Conclusion: Many studies proved the positive role of pharmacists’ interventions on medication adherence especially patient education and counseling, but they were not strong evidence, and this is not enough to prove their important role. So more validated and reliable studies must be conducted in this field to give more reliable results.