The burdens of tuberculosis (TB) and diabetes mellitus (DM) in Nigeria are high. DM often goes unrecognized in TB patients, resulting in poorer treatment outcomes compared with TB patients only. This study set out to compare TB treatment outcomes and associated factors in TB only and TBDM patients when a collaborative care (CC) model is in place.A prospective quasi-experimental study, modeled after the World Health Organization and The Union's Collaborative Framework for Care and Control of TB and DM was carried out among TB patients in two chest clinics in Lagos state. Patients were grouped into TB only, who received the usual TB care, directly observed treatment, short course (DOTS), and TBDM, who received DOTS and CC. Data were analyzed with IBM Statistical Package for the Social Sciences, version 23.0. Chi-square and multivariate analysis determined the association between treatment success and CC. Statistical tests were calculated at 95% confidence intervals and considered significant when P value is < 0.05.Of 671 participants in the study, 52 (7.7%) had DM. At TB treatment completion, there was no statistically significant difference in outcomes between TBDM and TB-only patients (P = 0.40). Patients who received CC were about 32 (OR: 31.60, 95% CI: 3.38-293), and 5 times (OR: 5.08, 95% CI: 1.35-19.17) more likely to achieve success and cure, respectively, compared to those who did not.Provision of CC with DOTS ensured improved TB treatment outcomes in TBDM patients. Recommendations of WHO/The Union are feasible in our setting.