Background/Objectives: Chronic diseases, such as diabetes mellitus, require sustained management and medication adherence to reduce the risk of related complications and mortality. However, the adherence levels are not satisfactory, which could be attributed to several factors, including cultural beliefs and socioeconomic factors. This study aimed to assess the relationship between cultural and socioeconomic factors, patient preferences, and medication adherence among diabetic patients. Methods: A mixed-methods cross-sectional design was implemented using face-to-face questionnaires and personal interviews. This study was conducted in 159 primary healthcare clinics (PHCs) in Madinah, Saudi Arabia, from 26 August 2024 to 10 February 2025. It included type 1 and type 2 diabetic patients. The Morisky Medication Adherence and General Medication Adherence Scales were used to evaluate diabetes medication adherence among the participants. Results: The included 424 diabetic patients had a predominant age range from 40 to 59 (48.1%). The majority were non-smokers (88.7%), Saudi Arabian (94.6%), and female (62.7%). The findings revealed a significant association between patient age (p < 0.001), body weight (p = 0.023), nationality (p = 0.015), educational level (p = 0.027), and the presence of comorbidities (p = 0.005) with the level of medication adherence. Conclusions: This study revealed that most diabetic patients attending PHCs in Madinah exhibited medium-to-high levels of medication adherence, with key influencing factors including age, comorbidities, education level, physician satisfaction, and health self-awareness.