Introduction: Dental caries is a disease caused by the interaction of several factors, including diet, since the development of the biological environment that promotes cariogenic bacterial metabolism often depends on it. Objectives: To determine the prevalence of caries in preschool children from Huaura, Peru, and to confirm if there is an association between their salivary pH and body mass index (BMI) and the level of knowledge about oral health of one of their parents. Materials and methods: A non-experimental, correlational, and cross-sectional study was conducted in 126 preschoolers equally distributed in 3 age groups (3, 4, and 5 years old). The association between the presence of caries and the variables considered was determined by means of the chi-square test of independence, with a confidence level of 95% and a type I error of 5%. In addition, a multiple logistic regression analysis was performed to calculate the probability of caries development in relation to each risk factor. Results: The prevalence of caries was 80.2% (95%CI:73.2-87.2); furthermore, salivary pH (p=0.012) and the level of parental knowledge (p<0.001) were significantly associated with caries occurrence. Regarding the multiple regression analysis, an OR=0.12 (95%CI:0.02-0.63) was obtained for pH and an OR=0.50 (95%CI:0.35-0.74) for the level of parental knowledge in relation to the probability of caries development. Conclusion: The level of parental knowledge about oral health and high salivary pH levels of preschoolers were protective factors against caries development in the study population. On the other hand, no association was found between BMI and the presence of caries in 5-year-old preschoolers.