This article aims to present general methodological aspects of the Brazilian National Survey on Child Nutrition (ENANI-2019), from the conception of the study design to details of the data collection. This is a household-based population survey with a sample calculated at 15,000 households to identify children under five years of age, conducted in 123 municipalities in Brazil's 26 states and the Federal District. ENANI-2019 includes data on breastfeeding and dietary intake; anthropometric nutritional status of all children and their biological mothers; and nutritional status concerning the following micronutrients: iron (hemoglobin and ferritin), zinc, selenium, and vitamins A, B1, B6, B12, D, E, and folic acid of children from 6 to 59 months of age. A total of 193,212 households were visited, of which 19,951 were eligible, and 12,524 were included in the study. A total of 14,558 children were studied, of whom 13,990 (96.1%) and 13,921 (95.6%) had their body mass and length/stature measured, respectively, and 14,541 (99.9%) underwent 24-hour dietary recalls (24HR). Of the 12,598 children eligible for blood sample collection, 8,739 (69.3%) had at least one laboratory parameter measured. Data were collected from February 2019 to March 2020, when the survey was interrupted due to the COVID-19 pandemic. The evidence produced by the ENANI-2019 survey can back the formulation, follow-up, and/or reorientation of food and nutrition policies such as the promotion of breastfeeding and healthy eating and the prevention and control of different forms of malnutrition.