Objective This study aimed to assess the prevalence of diabetic macular oedema and its associated factors among adult patients with diabetes attending comprehensive specialised hospitals in Northwest Ethiopia in 2023.Design An institution-based, cross-sectional study.Setting The study was conducted at the University of Gondar, Felege Hiwot and Debre Markos comprehensive specialised hospitals in Northwest Ethiopia from 8 May to 15 June 2023.Participants This study was conducted on 890 adult patients with diabetes selected using a systematic random sampling technique.Outcome measures Participants with diabetic macular oedema were assessed using slit lamp biomicroscopy with a +90 dioptre Volk lens. Blood glucose levels were measured by fasting blood sugar tests. Data were collected through physical examination, review of medical records and face-to-face interview.Results Among a total of 890 study participants, the prevalence of diabetic macular oedema was 25.8% (95% CI 23.1 to 28.8). Peripheral neuropathy (adjusted OR (AOR)=3.02, 95% CI 1.76 to 5.29), hypertension (AOR=1.98, 95% CI 1.24 to 3.17), poor blood glucose control (AOR=5.06, 95% CI 2.95 to 8.67), obesity (AOR=5.03, 95% CI 2.50 to 10.13), longer duration of diabetes mellitus (AOR=3.78, 95% CI 2.21 to 6.24) and poor adherence to diabetic medication (AOR=2.06, 95% CI 1.32 to 3.28) were significantly associated with diabetic macular oedema.Conclusion In Northwest Ethiopia, a quarter of patients with diabetes were found to have diabetic macular oedema. Factors such as peripheral neuropathy, hypertension, poor blood glucose levels, obesity, long duration of diabetes mellitus and poor adherence to diabetic medications were significantly associated with diabetic macular oedema. Improvement of glucose control and exercise for optimal body weight maintenance are recommended to prevent the development of diabetic macular oedema.