In studies of animal behavior, a detailed description of behavioral displays of a species—the ethogram—is a fundamental step in order to evaluate inter- and intra-sexual interactions. It can also assist in comparative studies by helping to determine derived and plesiomorphic behaviors of a taxon. Behavioral repertoires of lizards have been studied within different contexts, both in field and in laboratory. The striped lava lizard, Tropidurus semitaeniatus, has been studied in its natural history, trophic ecology and autoecology. However, there are no detailed studies of its behavior. Here, we produced a detailed ethogram for the species and describe a new behavior, the dorsum display, an unknown behavior not reported in any Tropiduridae to date. We described agonistic behaviors from recordings of interaction trials in the laboratory. The most frequently displayed behaviors were tongue-flicking, bite, intimidation posture and head bob, among others. We present supplemental material with videos of all displayed behaviors.