Objective: Advances in geospatial technologies have recognized the role of geographic distance as a barrier to healthcare accessibility. Frequent transportation is supposed to buffer issues with distance, while infrequent services impede the uptake of care. The role of public transportation on the accessibility of health care-including oral health care-is not well elucidated in the context of megacities, such as the municipality of São Paulo, Brazil. This study aimed to compare the supply of public transportation to primary dental clinics and the population between advantaged and disadvantaged areas in São Paulo city. Methods: A total of 4101 primary dental clinics in São Paulo city were identified and geocoded. Geographic coordinates were also retrieved for the 19 242 bus stops, 56 commuter rail stations and 64 rapid transit stations. Clinic locations and transport points were integrated with the city's 19 128 constituent census tracts-each containing sociodemographic data on the 11 252 204 residents-using Geographic Information Systems (GIS). Results: Almost all clinics were located within 0.5 km of public transportation. Half of all clinics were within 0.5 km of high-frequency transport points, and three-quarters were within 1 km. Likewise, 99% of the population resided within 0.5 km of any public transportation. However, only 22% were within 0.5 km of high-frequency options, and half were within 1 km. Those within 0.5 km of high-frequency points had higher average monthly household incomes and lower illiteracy rates, with lower proportions of children and ethnic minorities, and higher proportions of older people. Conclusion: Clinics and populations in sociodemographically disadvantaged tracts have poorer public transportation links in São Paulo city.