Background: Diabetes mellitus (DM) is the most common chronic disorder among the Saudi population; it reaches up to 20% of the population. Alternative medicine (AM) use among the Saudi population is more common among the elderly due to some beliefs. This study aimed to assess the prevalence of AM use among diabetic patients and their adverse effects, and to raise awareness about these acts. Methods: A cross-sectional study was conducted to assess the use of AM among diabetic patients in Al Kharj, Saudi Arabia. We interviewed 558 people with diabetes of both genders and all ages in hospitals and primary care clinics in Al Kharj, Saudi Arabia. Results: A total of 558 diabetic patients participated in the present study. Most included patients (61.6%) were type II DM. Only 17.9% of the patients were using AM, while 66.4% were not, and 15.7% had used AM prior. Only 4.7% of the diabetic patients preferred AM use, while 24.4% preferred modern medicine use. 12.8% of the participants reported that AM could cause adverse effects. Most patients were regular in drug use (70%), while only 6.8% were not committed to drug use. Conclusion: The present study found the prevalence of AM use among diabetic patients to be 17.9%. Only 4.7% of the diabetic patients preferred AM use. The most used AM were fennel flower, honey, and herbs. Gender and education were significant factors in AM use among diabetic patients.