Both tuberculosis (TB) and diabetes mellitus (DM) are major global public health concerns, and their prevalence has been rising rapidly in developing countries like Ethiopia. A challenge to TB control could arise from the rising incidence of diabetes and undermine efforts to eradicate the disease. In Ethiopia, particularly in the research region, there is a lack of data regarding TB-DM comorbidity and associated risk factors. To assess the prevalence and determinants of DM in patients with tuberculosis at South Gondar Zone Hospitals in Ethiopia. A facility-based cross-sectional study was conducted in South Gondar Zone health facilities from December, 2023 to May 2024. A total of 1174 participants were selected using a systematic sampling technique. The data were collected using an interviewer-administered structural questionnaire. Previously and newly diagnosed TB at any stage of anti-TB treatment were subjected to a fasting blood sugar measurement. The collected data was entered into EPI Data 3.1 and exported to SPSS version 24 for analysis. To determine the risk factors, logistic regression was employed. An odds ratio with a 95% CI and a P-value <
0.05 were used to declare statistical significance. The prevalence of diabetes mellitus and prediabetes was found to be 9.8% (95% CI: 7.1-1.35) and 13.5% (95% CI: 11.4-16.1), respectively. TB patients aged 40-50 years (AOR = 3.65, 95% CI: 1.32-10.14), >
50 years of age (AOR = 5.65, 95% CI: 2.01-16.35), being married (AOR = 3.68, 95% CI: 2.31-7.2), having no formal education (AOR = 3.87, 95% CI: 1.21-9.2), and being overweight or obese (AOR = 3.41, 95% CI: 1.85-8.62) were significantly associated with diabetes mellitus. The prevalence of DM among TB patients in our study was high. Older age, being married, having no formal education, and being overweight or obese were significant risk factors for TB. Integrating TB and DM screening as well as care delivery in clinical practice is essential to achieving the goal of TB control and improving the health outcomes of both diseases.