Purpose: Optimal adherence to antidiabetics among patients with type 2 diabetes mellitus has been associated with positive health outcomes; however, studies to assess this adherence in Saudi Arabia are scarce. We aimed to evaluate adherence to antidiabetics using a Saudi population. Methods: This was a multicenter, retrospective cohort study of patients (≥ 18 years old) with type 2 diabetes mellitus who received ≥ 1 antidiabetic between 2015 and 2020. Adherence was estimated using the continuous multiple-interval measure of medication availability (CMA7). A CMA7 cutoff point of ≥ 80% was chosen to define optimal adherence, and the odds of not achieving therapeutic annual HbA1c levels (i.e. ≥ 7%) in the optimal vs. suboptimal adherence groups was assessed using a logistic regression model adjusting for the measured confounders. Results: A total of 36,789 patients were included in the study. The most commonly prescribed regimens were metformin single treatment (n=15,025 [41.6%]) and gliclazide-metformin combination treatment (n=5,667 [15.7%]). The median CMA7 was 70.4%, and only 13,552 (36.9%) patients were adherent to their antidiabetics (CMA7 ≥ 80%). The odds of not achieving therapeutic HbA1c levels one year after the index date were comparable in the optimal vs. suboptimal adherence groups (odds ratio = 0.99, 95% confidence interval 0.92 to 1.05). Conclusions: This study showed that a large proportion of a Saudi population with type 2 diabetes mellitus were non-adherent to their antidiabetic treatments. Future Saudi and regional studies are needed to assess the impact of adherence on HbA1c levels and on cardiovascular outcomes.