In most maternity units, the physician classifies, evaluates, and determines which unit will receive the newborn (NB) after birth. Evaluation occurs in the delivery room, taking into consideration the following factors: birth weight, gestational age, and behaviors that define the clinical picture and disease. This observational study evaluates the reliability of an NB classification instrument. The study was conducted at the nursery of a public hospital in São Paulo. Nine nurses applied the instrument to 63 NB, with two of the nurses working simultaneously in each of the nursery's five sectors. The Kappa level of agreement among the nurses was found to be excellent for most care areas (69.0%). It was concluded that there was a consensus and agreement among the nurses that the instrument was complete, easy to understand and applicable, but was very time consuming. The nurses recognize the instrument's importance for the allocation of professionals, organization, and care planning.