Purpose: To develop an in-depth understanding of the barriers to medication adherence among patients with uncontrolled diabetes attending primary health care (PHC) centers in Qatar by exploring and integrating patients’ and health care providers’ perspectives. Participants and methods: A descriptive qualitative methodology was used in this study. A trained researcher conducted semi-structured face-to-face interviews at two PHC centers. Patients with uncontrolled diabetes (with varied sociodemographic characteristics) and their respective health care providers (physicians, pharmacists, nurses, dieticians, and others) were purposively selected from the two PHC centers. All interviews were audio recorded, transcribed verbatim, and analyzed using thematic content analysis. Results: Thirty interviews (14 patients and 16 health care providers) were conducted. A number of barriers to medication adherence were identified and classified broadly under three main themes: 1) patient-related factors, which included patients’ individual characteristics and patients’ perception, attitude, and behavior; 2) patient–provider factors, which included communication and having multiple health care providers caring for the patient; and 3) societal and environmental factors, which included social pressure and traveling to visit friends and relatives. Conclusion: Patients with uncontrolled diabetes face multiple barriers to medication adherence. Similar themes emerged from both patients and their care providers. This research highlights the need for concerted multidimensional efforts and series of interventions to overcome these barriers. One vital intervention is expanding the scope of pharmacists’ role within the PHC centers through providing medication reconciliation, patient-tailored medication counseling, and medicines use review, which may improve treatment outcomes among patients with diabetes. © 2018 Jaam et al.