Objective: The purpose of the study was to identify dental fluorosis prevalence and to analyze its association with tap water fluoride concentration and beverage consumption in school children from the city of Oaxaca, who were receiving fluoridated salt. Study design: A cross-sectional study was performed on elementary public school children. Dean's Index was applied to assess dental fluorosis. The parents of the children who were studied completed a questionnaire about socio-demographic characteristics and type of beverages consumed by their children. A total of 917 school children participated in this study. Results: Dental fluorosis prevalence was 80.8%. The most frequent fluorosis category was very mild (41.0%), and 16.4% of the children were in the mild category. The mean water fluoride concentration was 0.43 ppm (±0.12). No association was detected between tap water fluoride concentration and fluorosis severity. The multinomial regression model showed an association among the mild fluorosis category and age (OR = 1.25, [95%CI 1.04, 1.50]) and better socio-economic status (OR = 1.78, [95%CI 1.21, 2.60]), controlling for fluoride concentration in water. Moderate and severe fluorosis were associated with soft drink consumption (OR = 2.26, [95%IC 1.01, 5.09]), controlling for age, socio-economic status, and water fluoride concentration. Conclusions: The prevalence of fluorosis was high. Mild fluorosis was associated with higher socio-economic status, while higher fluorosis severity was associated with soft drink consumption.