The objective of this work was to estimate the prevalence and severity of erosive tooth wear (ETW), and to identify risk indicators of deciduous dentition of a group of schoolchildren from public schools in Tlalnepantla de Baz, State of Mexico. A cross-sectional study was carried out in 352 schoolchildren from 5 to 7 years old. The severity of the ETW was evaluated using the Basic Erosive Wear Examination (BEWE). Risk indicators were evaluated through a survey which included food and beverage consumption, consumption habits, vitamin C consumption, gastroesophageal reflux, heartburn, belching, xerostomia, vomiting and teeth grinding. Multinomial logistic regression models were fitted. The prevalence of ETW was 99.7% (n = 351). Regarding severity, 46.6% were at a null/mild level, 27.3% moderate, and 26.1% severe. Males were more likely to present severe ETW (odds ratio (OR) = 2.23, 95% confidence interval (CI), 1.27–3.93; p = 0.005). The risk indicators for the severity of ETW were the frequent consumption of citrus fruits (OR = 2.09, 95% CI, 1.12–3.89; p = 0.021), fruit juice (OR = 1.99, 95% CI, 1.06–3.75; p = 0.033), processed beverages (OR = 2.15, 95%CI, 1.23–3.78; p = 0.008) and hot sauce (OR = 1.82, 95% CI, 1.03–3.20; p = 0.036). The prevalence of ETW in the deciduous dentition was very high (99.7%) and ~1/3 for severe ETW. The dietary factors associated with severe ETW are part of the regular consumption of Mexican school-age children, which impact their oral health condition. It is important to establish intervention strategies from the infant stage, focused on both children and their caregivers.