Hypertensive patients' knowledge and adherence to prescribed medicines are critical in managing their condition, as poor adherence may lead to adverse cardiac and cerebrovascular events. The present study assessed hypertension-related knowledge and medication adherence among hypertensive patients attending primary health centers (PHCs) in the Aljouf Province, Saudi Arabia. Using a cross-sectional design, we conducted this survey on 390 patients. Self-reported hypertension knowledge was assessed using the Hypertension Knowledge Level Scale (HK-LS), and medication adherence was determined using the Hill-Bone Medication Adherence Scale. We used binomial regression analysis (adjusted with other variables) to find the associated factors of medication adherence. This study found that nearly half (49.2%) of the participants had inadequate knowledge, and poor medication adherence was noted in 40.8% of the participants. We found a positive correlation between HK-LS and the Hill-Bone Medication Adherence Scale scores (Spearman's rho = 0.312, = 0.002). Medication adherence was significantly associated with job status (private sector (ref: public sector, adjusted odds ratio [AOR] = 2.02, 95% CI = 1.18-3.62, = 0.005)), living in an urban region (ref: rural, AOR = 3.61, 95% CI = 1.85-5.72, = 0.002), and duration since diagnosis of more than 5 years (ref: ≤1 year, AOR = 3.53, 95% CI = 2.36-4.95, = 0.001). The present study findings indicate that there is still a critical gap in managing hypertension at the PHCs in this region, and this may lead to poor health outcomes among the patients and burden the healthcare system. Hence, continuous patient education and targeted counseling are recommended for those with poor medication adherence.