Background: 99DOTS is a cellphone-based digital adherence technology. The state of Himachal Pradesh, India, made 99DOTS available to all adult patients with drug-sensitive tuberculosis (TB) in May 2018. While 99DOTS has engaged over 300,000 patients across India, few studies have evaluated its impact on TB treatment outcomes. Methods: We compared treatment outcomes of adult patients with drug-sensitive TB before and after Himachal Pradesh’s 99DOTS launch using data from India’s national TB database. Pre-intervention group patients initiated treatment between February and October 2017 (N=7722), and post-intervention group patients between July 2018 and March 2019 (N=8322). We analyzed patient engagement with 99DOTS and used multivariable logistic regression to estimate impact on treatment outcomes. Results: 2746 (33.0%) post-intervention group patients called 99DOTS at least once, on average calling on 58.5% of treatment days. In the pre-intervention group, 7186 (93.1%) had favorable treatment outcomes, compared to 7734 (92.9%) in the post-intervention group. This difference was not statistically significant (OR=0.981, 95%CI 0.869-1.108), including after controlling for patient characteristics (adjusted OR=0.970, 95%CI 0.854-1.102). Conclusions: We found no statistically significant difference in treatment outcomes before and after a large-scale implementation of 99DOTS. This result can be informative for programs seeking to design and prioritize impactful adherence interventions.