-The black-eyed leaf frog (Agalychnis moreletii) is a critically endangered hylid frog restricted to humid lowland and lower montane forests of southern Mexico and northern Central America. Very few reports exist on wild reproductive behavior of this species. Lower body tremulation display has been reported as a relevant part of agonistic interactions between males of the related species A. callidryas but has never been reported in other species of Agalychnis. Herein, we present the first report and description of this tremulation display among males of A. moreletii in a lower montane forest of Guatemala. Based on our observations, we suggest that this display may serve to prevent physical confrontations among males and might play an important role in defining territories. We also suggest that the difference in fundamental frequency of the tremulations between A. moreletii and A. callidryas may serve to avoid confusing signals between species where they breed sympatrically.