Background Pre-treatment loss to follow-up (PTLFU) among tuberculosis (TB) patients is a global public health problem, because such patients are highly infectious and experience high mortality. There is no published evidence on this issue from Myanmar. Objective To determine PTLFU and treatment delays (> 7 days duration between the date of diagnosis and starting anti-TB treatment) and their associated demographic, clinical, and health system-related factors among bacteriologically confirmed (sputum smear-positive and/or Xpert-positive) TB patients diagnosed in public health facilities of the Mandalay Region between January and June 2017. Method This was a cohort study involving secondary analysis of routine programme data. Every bacteriologically confirmed TB patient in the laboratory register was tracked for at least 3 months in the treatment register. Patients neither found in the treatment register nor referred out for treatment were considered PTLFU. Results Of the 1365 bacteriologically confirmed patients diagnosed, 1051 (77%) started on anti-TB treatment, 200 (15.6%) were referred for treatment to health facilities outside the study area, and 114 (8.4%, 95% CI 7.0%–9.9%) did not initiate anti-TB treatment (PTLFU). PTLFU was significantly higher in those with TB/HIV co-infected (18%), sputum smear-negative but Xpert MTB-positive patients (31%), and patients diagnosed at a moderate- or high-volume facility (> 50 patients tested form TB during the study period) (~ 10%). Of the 940 patients with dates recorded, 46 (5%) had a treatment delay of more than 7 days. Patients aged 45–64 years had higher risk of treatment delay compared to those aged 15–44 years. About 97% of records did not have a phone number recorded. Conclusion PTLFU and treatment delay were relatively low in the Mandalay Region. While this is reassuring, urgent steps must be taken to address those that are lost, which includes improving documentation of phone numbers to improve ‘trackability’, instituting proactive measures to trace patients lost in the care pathway, and introducing an indicator in the national tuberculosis programme (NTP) monthly report to monitor and review PTLFU. Patient subgroups with higher PTLFU should receive priority attention.