Background: Medication adherence plays a crucial role in determining treatment success and overall health outcomes, yet non-adherence rates remain high across various patient populations. Factors contributing to poor adherence are multifaceted, including patient, healthcare system, and socioeconomic factors. The consequences of non-adherence are significant, leading to increased healthcare costs, hospitalizations, and poorer health outcomes. Developing interventions to promote adherence is essential to address this challenge. Objective: This review aims to provide a comprehensive overview of the current literature on medication adherence, identifying key factors influencing adherence, exploring the effectiveness of interventions, and highlighting implications for clinical practice and policy. By synthesizing existing evidence, the review seeks to address the complex barriers to adherence and improve health outcomes. Conclusion: Understanding the factors influencing medication adherence, such as socioeconomic status, healthcare system complexity, condition nature, therapy regimen, and patient beliefs, is critical for developing effective interventions. Strategies to improve adherence include simplifying regimens, patient education, family involvement, technology-based interventions, and medication management programs. Studies in Saudi Arabia highlight the importance of addressing medication adherence to enhance health outcomes and reduce healthcare costs across various conditions. Promoting adherence through multifaceted approaches is essential for improving patient outcomes and reducing the burden of non-adherence on healthcare systems globally.