Gynandromorphism is a condition in which an organism exhibits both male and female characters simultaneously. This condition is the result of an abnormal process during embryonic development, and has been frequently reported in arthropods, especially crustaceans, insects, and arachnids. Here, we report a case of gynandromorphism in the brown dog tick, Rhipicephalus sanguineus s.l. in Colombia. The individual was collected from a domestic dog in the municipality of Samaná, Department of Caldas, in the inter-Andean Valley of the Magdalena River Basin of the country. This record is the first documented for this species in Colombia, and the fourth in America where this anomaly was previously reported in countries such as Brazil (two cases) and Mexico (one case).