ABSTRACT Objective To evaluate the association between the availability of GeneXpert ® MTB/RIF in municipalities and the proportion of people who have access to this diagnostic technology for tuberculosis (TB), as well as the resistance detected by the surveillance system in Brazil. Methods We analyzed 4,998 Brazilian municipalities that reported 432,937 new TB cases between 2015 and 2020. We compared municipalities with and without the availability of GeneXpert ® MTB/RIF regarding the prevalence of effective access to GeneXpert ® MTB/RIF diagnosis and that of detected resistance. Results Municipalities with at least one GeneXpert ® MTB/RIF system had three times (95%CI 2.9-3.0) the access to diagnostic tests and 80.4% (95%CI 70.6%-90.2%) higher detection of resistance, compared to municipalities without this technology. We estimate that there have been 2,110 cases of undetected resistance during this period in the country. Conclusions The availability of GeneXpert ® MTB/RIF system in the municipality increased the sensitivity of the surveillance for detecting TB resistance. Public Health implications It is a priority to strengthen laboratory networks and narrow the gap in access to rapid diagnosis in remote areas to improve the detection and control of drug-resistant tuberculosis.