Objective: To identify the occurrence of overweight and obesity in preschool children (two to five years) in a day-care center in the city of São Paulo, using the weight/height ratio. Methods: This is a descriptive study, with exploratory quantitative approach, conducted in a day-care center in São Paulo. The sample consisted of 29 children, aged from two to five years and the data were collected through questionnaires. Rresults: As for the nutritional assessment of children according to the Waterlow criteria, 12 (41%) were normal, 7 (24%) obese, 5 (17%) overweight, 3 (10%) had grade 1 malnutrition, 1 (4%), morbid obesity and 1 (4%), grade 3 malnutrition. Cconclusions: It is concluded that a significant proportion of the children assessed is above the appropriate weight range, requiring the implementation of preventive actions aimed to guide habits of good nutrition, encouraging physical activity, thereby decreasing the rates of child obesity and impacting their health at adulthood.