Humans introduce non‐native species by means such as the deliberate release of fish into fresh waters and through commercial trade. The guppy Poecilia reticulata Peters, 1859, is commonly kept in aquaria and controls disease vectors, and now it occurs in many areas outside its natural distribution. Its initial habitat in Brazil was identified, and a study was performed to determine whether the density of guppies can be explained by the density of human population, per‐capita gross domestic product, level of human impact on the areas where guppies have been found and fish‐sampling effort. A total of 1402 guppy records were found; the southeastern region had the oldest records; and the southeastern, northeastern and central‐western regions had the maximum records. Low tolerance to the colder climate may be the reason for the lack of guppy records in the southernmost states. It was also observed that the occurrence of this fish is positively, yet weakly, related to the density of human population, indicating that improved regulations regarding its use in controlling disease vectors, the aquarium trade and education of aquarium hobbyists could help prevent the spread of this species and its potential impacts in Brazil.