Introduction:The adherence level to antihypertensive medication is a neglected topic in academic research in Saudi Arabia; however, there are a number of international studies that shed light on the level of patient adherence to medication. Aim: This study aimed to determine patients' knowledge and medication adherence among hypertensive patients. Patients and methods: This is a cross-sectional study conducted among hypertensive patients in Saudi Arabia. An Arabic translation for a self-administered questionnaire was distributed among patients with hypertension (HTN). Results: 698 hypertensive patients took part in the study (59.2% females, 40.8% males). The incidence of patients with hypertensive complications was 39.4%. The mean knowledge score was 47.9% (SD 21.4) while the overall mean adherence score was 75.4 (SD 16.5). Factors associated with increased score of knowledge and adherence were age group >45 years, female gender, being unemployed, earning more than 10,000 SAR monthly, being a non-smoker, diagnosed with HTN for 5 years or more, and regular doctor visits. Conclusion: The patient's compliance with HTN medication is good, but the understanding of their own disease is poor.