Patients' health beliefs are essential to improve medication adherence among patients with hypertension. Our objective was to examine the relationship between (1) patients' beliefs about hypertension, medication, and self-efficacy and medication adherence and (2) medication adherence and blood pressure control in Oman. This cross-sectional study included 215 participants with hypertension. Participants completed 4 questionnaires (Arabic version) to measure medication adherence, beliefs about hypertension severity, beliefs about medication, and self-efficacy. Bivariate and multivariate logistic regression was used to conduct the analyses. Higher self-efficacy (odds ratio [OR], 2.59; 95% confidence interval [CI], 1.54-4.37), stronger beliefs about medication necessity (OR, 1.98; 95% CI, 1.21-3.23), increased age (OR, 1.06; 95% CI, 1.03-1.10), and fewer medication concerns (OR, 0.34; 95% CI, 0.20-0.57) were related to high medication adherence. Moreover, uncontrolled blood pressure was less likely in participants with high medication adherence (OR, 0.47; 95% CI, 0.24-0.93). Patients' beliefs are important consideration to improve medication adherence. Clinically, patients' beliefs should be assessed, and strategies to improve medication adherence should incorporate beliefs as a key component to improve antihypertensive medication adherence. Patient education and counseling regarding hypertension and necessity and side effects of medications are important to maximize positive beliefs and improve medication adherence.