The objective of this study was to evaluate the feeding behavior of feedlot-finished young bulls fed diets containing peanut cake instead of soybean meal. A total of 32 Nellore young bulls with an initial body weight of 390 ± 43.5 kg were distributed in a completely randomized design. The animals were individually housed in stalls and fed Tifton 85 hay with four concentrate mixtures containing 0, 33, 66, or 100% peanut cake substituting for soybean meal. The diets were formulated to be isonitrogenous (with 15% crude protein) and isocaloric (with 65% total digestible nutrients), with a 40:60 forage:concentrate ratio, in the form of total mixed diet. The experimental period was 90 days, and data were collected every 28 days. Feeding behavior was assessed by means of observation and recording of the daily time spent feeding, ruminating, and idling, quantification of the periods and calculation of variables related to mastication characteristics as well as feeding and rumination efficiencies. Substitution of soybean meal for peanut cake in the diets caused a linear decrease in the intake of dry matter and neutral detergent fiber but did not affect the behavioral activities of the young bulls. Peanut cake may therefore replace up to 100% of soybean meal in the diet of feedlot-finished young Nellore bulls because it does not affect the feeding behavior of these animals.