Babassu (Orbignya phalerata Mart.) is a palm tree native to Brazil’s northeast and north states that appears between Cerrado and the Amazon rain forest. Usually, each tree produces 15 to 25 bunches of fruit, each fruit weighting 98 to 280 g. The average weights of each component of the babassu coconut are 11% exocarp, 23% mesocarp, 59% endocarp and 7% kernels. From mesocarp can be extracted a flour, whose composition is 60% starch. The use of babassu flour starch can be used as an energy source for ruminants, however because of composition, it is important to study the feeding behavior. Twenty crossbred lambs (initial BW of 21.6 ± 3.5 kg and 120 d old) were used in a randomized complete block design according to initial BW and age. Lambs were penned individually during 50 d and fed an isonitrogenous diet (16.5 ± 0.2 CP, DM basis) containing 70% concentrate and 30% coastcross hay. Increasing levels of BSF were 0, 10, 20 and 30%, DM basis, corresponding to the experimental diets BFS0, BFS10, BFS20 and BFS30, respectively. Animals were monitored every 5 min during 24 h, on the 25th day of the experiment, according to the activities: eating, rumination, idle and other activities. The feed and rumination efficiencies, expressed as g DM/hour were obtained by dividing the average daily intake of DM by the total time spent eating and ruminating in 24 h, respectively. Orthogonal polynomials for diet responses were determined by linear and quadratic effects. Effects were declared significant at P ≤ 0.05. There was a quadratic response (P ≤ 0.05) for time spent in eating (164.0, 231.0, 270.0 and 250.0 min/d for BFS0, BFS10, BFS20 and BFS30), time spent in other activities (289.0, 206.0, 179.0 and 168.0 min/d for BFS0, BFS10, BFS20 and BFS30) and eating efficiency on DM (402.9, 331.6, 234.5 and 180.7 g DM/hour for BFS0, BFS10, BFS20 and BFS30). The increasing levels of BFS did not affect (P ≥ 0.05) the time spent in rumination, rumination efficiency and time spent in idle. It is concluded that increasing BFS levels changed the feeding behavior of lambs, especially for time spent for eating and feed efficiency.