In many snakes, males engage in agonistic interactions (male–male combat) apparently to establish dominant–subordinate relationships to gain priority access to reproductive females. In the Neotropical genus Bothrops Wagler, 1824 (∼45 species), male–male combat has been recorded only in three species of the monophyletic Bothrops atrox group. However, most male combats recorded in this clade occurred in captivity, an environment that facilitates the emergence of agonistic interactions. Here, we provide the first record of male–male combat in free-ranging Amazonian Common Lanceheads (Bothrops atrox (Linnaeus, 1758)) and discuss the implications of this observation for the species mating system. During fieldwork, we found one immature female and five active adult males, two of them fighting. These observations suggest that reproductive male B. atrox actively search and compete for widely dispersed and scarce receptive females.