Nicarbazin is an anticoccidial drug used mainly in birds, but also in rabbits. Besides the anticoccidial activity, riicarbazin has shown several other effects such as inhibition of growth and feed efficiency in poultries, and stimulation o f sugar intestinal absorption in rabbits. The present work has been performed in order to check whether nicarbazin also affects L‐leucine intestinal absorption. The results obtained show that nicarbazin decreases L‐leucine accumulation in the jejunal tissue, and increases mucosal to serosal transepithelial fluxes o f this amino acid in a dose‐dependent way, without modifying its diffusion across the intestinal epithelium. The drug stimulates the amino acid uptake in brush‐border and basolateral membrane vesicles, thus suggesting that nicarlxizin increases the absorption of L‐leucine mediated by