In India, an estimated 50% of tuberculosis (TB) patients are diagnosed and managed by private providers (PPs). However, there is limited information on treatment outcomes among those treated by PPs largely because of a lack of systems for patient follow-up and documentation of the outcomes. Tuberculosis Health Action Learning Initiative (THALI) project implemented in six districts of West Bengal, supported PPs in managing TB patients and systematically documented the TB treatment outcomes of such patients. This provided us an opportunity to describe the treatment outcomes and assess factors associated with 'unsuccessful outcomes' among TB patients notified by PPs from January to April 2018. This was a retrospective cohort study using routinely collected data. During the study reference period, 2347 patients were notified from 389 PPs. The patient's mean (SD) age was 39.9 (17.2) years and 61% were males. Of the total, about 86% had pulmonary TB, 95% were new cases, and 23% were microbiologically confirmed (either on sputum smear microscopy or Xpert assay). Among 2347 patients, 19% received free drugs from the National Tuberculosis Program (NTP) under the supervision of PPs while the rest purchased anti-TB drugs from the private pharmacies. The 'successful outcomes' (cured and treatment completed) were seen in 86.1% (95% confidence interval (CI), 84.6%-87.4%) patients and 8.6% were 'not evaluated'. The patients who received free NTP drugs (adjusted relative risk-4.0 (95% CI: 3.1-5.0)) had a higher risk of 'unsuccessful outcomes' than those who availed of drugs from private pharmacies. The high 'successful outcomes' among TB patients treated by PPs are promising. However, higher 'unsuccessful outcomes' among patients on free NTP drugs need to be explored, and suitable corrective actions have to be taken.