ABSTRACT.- The aim of this study was to evaluate the effect of different factors on maternal protective behavior (MPB) of Nellore cows. A total of 3629 cows were evaluated around 24 h after calving, while their newborns were handled for navel care, ear tattoo and weighing. MPB was assessed by observing each cow reactions when its calf was caught in a corral pen. MPB score consisted of 5 levels, going from 1 (the cow paid no attention to the calf and remained indifferent to the procedure) to 5 (the cow showed aggressive behaviors toward the handler, trying to attack).