In Cambodia, the age-standardized prevalence of diabetes mellitus has increased in both men and women. The main objective of this study was to identify factors associated with diabetes medication adherence among people with diabetes mellitus in poor urban areas of Phnom Penh, Cambodia.A cross-sectional study was conducted in 2017 using a structured questionnaire for face-to-face interviews by trained interviewers. The participants were people with diabetes mellitus who were the active members of a peer educator network, lived in poor urban areas of Phnom Penh, and attended weekly educational sessions during the survey period. Diabetes medication adherence was measured using four items of modified Morisky Medication Adherence Scale. Participants were classified into two groups based on their adherence score: 0 (high adherence) and from 1 to 4 (medium or low adherence). Sociodemographic characteristics; medical history; accessibility to health services; and knowledge, attitude, and practices related to diabetes mellitus were examined. A multiple logistic regression analysis was conducted adjusting for sex, age, marital status, and education levels.Data from 773 people with diabetes were included in the analyses. Of the total, 49.3% had a high level of diabetes medication adherence. A high level of adherence was associated with higher family income (≥50 USD per month) (adjusted odds ratio [AOR] = 5.00, 95% confidence interval [CI] = 2.25-11.08), absence of diabetes mellitus-related complications (AOR = 1.66, 95% CI = 1.19-2.32), use of health services more than once per month (AOR = 2.87, 95% CI = 1.64-5.04), following special diet for diabetes mellitus (AOR = 1.81, 95% CI = 1.17-2.81), and absence of alcohol consumption (AOR = 13.67, 95% CI = 2.86-65.34).High diabetes medication adherence was associated with better family economic conditions, absence of diabetes mellitus-related complications, and healthy behaviors. It would be crucial to improve affordable access to regular follow-ups including promotion of healthy behaviors through health education and control of diabetes mellitus-related complications.