Medication adherence remains a major challenge in the management of type 2 diabetes mellitus (T2DM), yet the contribution of personality traits is insufficiently understood in Latin American populations. This cross-sectional analytical study examined associations between the Big Five personality traits and medication adherence among 92 adults with T2DM receiving outpatient care at the Regional Hospital of Moquegua in southern Peru during 2025. Personality traits were assessed using the 44-item Big Five Inventory, and adherence was measured with the eight-item Morisky Medication Adherence Scale. We evaluated associations using correlation analyses and binary logistic regression adjusted for age, sex, and diabetes duration, with bootstrap resampling and internal validation. Only 21.7\% of participants demonstrated optimal adherence, while 63.0\% had moderate adherence and 15.2\% had poor adherence. Higher conscientiousness (adjusted odds ratio [OR] = 3.62; 95\% confidence interval [CI]: 1.65--7.95) and agreeableness (OR = 2.62; 95\% CI: 1.37--5.02) were independently associated with greater odds of optimal adherence. In contrast, extraversion was inversely associated with optimal adherence (OR = 0.39; 95\% CI: 0.08--0.72). Neuroticism and openness to experience showed no statistically significant associations. These findings indicate that personality traits may complement clinical and sociodemographic factors in explaining medication-taking behavior among patients with T2DM. Person-centered interventions tailored to psychological profiles may help improve adherence, although longitudinal and multicenter studies are required to confirm these associations.
