PURPOSE: To assess the level of medication adherence and to investigate predictors of medication adherence and blood pressure control among hypertensive patients attending primary healthcare clinics in Makkah, Saudi Arabia. PATIENTS AND METHODS: Hypertensive patients meeting the eligibility criteria were recruited from eight primary care clinics between January and May 2016 for this study. The patients completed Arabic version of Morisky Medication Adherence Scale (MMAS-8), an eight-item validated, self-reported measure to assess medication adherence. A structured data collection form was used to record patients' sociodemographic, medical and medication data. RESULTS: Two hundred and four patients, of which 71.6% were females, participated in the study. Patients' mean age was 59.1 (SD 12.2). The mean number of medication used by patients was 4.4 (SD 1.89). More than half (110; 54%) of the patients were non-adherent to their medications (MMAS score < 6). Binary regression analysis showed that highly adherent patients (MMAS score = 8) were about five times (OR 4.91 [95%CI: 1.85-12.93; P = 0.01]) more likely to have controlled blood pressure compared to low adherent patients. Female gender (OR 0.40 [95% CI: 0.20-0.80; P = 0.01]), Age > 65 years (OR 2.0 [95% CI: 1.0-4.2; P = 0.04]), and being diabetic (OR 0.25 [95% CI: 0.1-0.6; P = 0.04]) were found to be independent predictors of medication adherence. CONCLUSION: Medication adherence is alarmingly low among hypertensive patients attending primary care clinics in Saudi Arabia which may partly explain observed poor blood pressure control. There is a clear need to educate patients about the importance of medication adherence and its impact on improving clinical outcomes. Future research should identify barriers to medication adherence among Saudi hypertensive patients.