Implementation studies are recommended to assess the feasibility and effectiveness of programmes. In Nigeria, little is known about the burden of diabetes mellitus (DM) among tuberculosis (TB) patients. The objective of this study was to determine screening efficacy, prevalence of DM and determinants of DM among TB patients. We report on a multi-centre implementation study carried-out in 13 health facilities in six States of Southern Nigeria. All newly diagnosed TB patients registered from March to October 2015 were screened for DM using current World Health Organisation guidelines. Overall, 2094 TB patients were evaluated, 196 (9.4%) were found to have DM. The prevalence of newly diagnosed DM was 5.5% (115/2094). DM prevalence varied according to age group; occurring in 2.2% of patients aged ≤ 25 years and 16.9% in patients aged (56-65) years. The additional yield of DM was 59% while the number needed to screen to detect a new case of DM was 18. Factors associated with DM were; age >40 years (aOR2.8, CI 2.1-3.9), rural residence (aOR2.3, 1.6-3.2), private health facility care (aOR2.0, 1.4-2.7), and having an occupation that engages in vigorous activity (aOR0.6, 0.4-0.9). The burden of DM among TB patients is high. Prioritization of DM screening for TB patients is indicated.