Aggregation among individuals of the same species is a common spatial pattern in nature, and has been well studied in insects, mammals, birds, and fishes. Among vertebrates, mammals, birds, and fishes are considered the most social. Among reptiles, snakes also form aggregations for mating, defense, or communal shedding, and this behavior can be associated to kin and conspecific recognition. Here, we report information on the aggregation behavior in Erythrolamprus poecilogyrus caesius. We made two observations in the Dry Chaco of Paraguay. In the first observation (2016) we found three adults of E. p. caesius under a fallen trunk. The second observation occurred in three temporary ponds (2020), where E. p. caesius aggregated in groups of five (juveniles), ten (juveniles and sub-adults), and two (juveniles). Aggregation can reduce predation risk, increase the survival or the reproductive success, and could occur in response to external cues. Future research must focus on aggregation context and define experimentally the factors that trigger it, and whether it depends on environmental resources, or if it is part of a social interaction.