BackgroundLesotho is one of the 30 countries with the highest tuberculosis incidence rates in the world, estimated at 650 per 100,000 population. Tuberculosis case detection is extremely low, particularly with the rapid spread of COVID-19, dropping from an estimated 51% in 2020 to 33% in 2021. The aim of this study is to understand the barriers to tuberculosis diagnosis and treatment completion.MethodsWe used a convergent mixed methods study design. We collected data on the number of clients reporting symptoms upon tuberculosis screening, their sputum test results, the number of clients diagnosed, and the number of clients who started treatment from one district hospital and one health center in Berea district, Lesotho. We conducted in-depth interviews and focus group discussions with 53 health workers and patients. We used a content analysis approach to analyze qualitative data and integrated quantitative and qualitative findings in a joint display.FindingsDuring March-August, 2019, 218 clients at the hospital and 292 clients at the health center reported tuberculosis symptoms. The full diagnostic testing process was completed for 66% of clients at the hospital and 68% at the health center. Among clients who initiated tuberculosis treatment, 68% (61/90) at the hospital and 74% (32/43) at the health center completed treatment. The main barriers to testing and treatment completion were challenges at sample collection, lack of decentralized diagnostic services, and socioeconomic factors such as food insecurity and high patient movement to search for jobs.ConclusionsTuberculosis diagnosis could be improved through the effective decentralization of laboratory services at the health facility level, and treatment completion could be improved by providing food and other forms of social support to patients.