Purpose: Cardiovascular diseases (CVDs) remain a global health threat, and medication adherence remains low. Medication adherence is a complex phenomenon and is affected by many factors that require investigation. Oman has limited literature examining medication adherence and influencing factors among patients with CVDs. This study examined the influence of health literacy, social support, the patient-physician relationship, and health-related quality of life on medication adherence among patients with cardiovascular diseases. Patients and Methods: This cross-sectional study used a correlation design. The study included 360 participants with CVDs. Descriptive statistics, independent t-test, one-way ANOVA, and multiple regression analysis were utilized for data analyses. Results: Findings revealed that higher social support (B=0.117; p=0.033), good patient-physician relationship (B=0.124; p 0.01), better mental health (B=0.045; p 0.01), more bodily pain (B=0.030; p 0.01), and unemployment (B=1.297; p 0.01) were predictors of higher adherence. High school education and above predicted lower medication adherence (B= −1.255; p= 0.019), while health literacy was not a significant predictor of medication adherence (B= 0.061; p= 0.289). Conclusion: To improve medication adherence, healthcare providers and researchers should consider improving patients’ social support, mental health, and the patient-physician relationship. In addition, patients’ socioeconomic status should always be considered and examined as an influencing factor of medication adherence.