Descriptions of morphological anomalies of phlebotomine sand flies (Diptera: Psychodidae) have been recorded in both the New World and the Old World. The majority of these anomalies are associated with the genitalia, the number of cibarial teeth, wing venation, the size of the palps, and other less significant features. Such morphological variations, particularly in symmetry, can result in incorrect species identification. The occurrence of gynandromorphism in sand flies is a rare phenomenon. Currently, only five such cases have been registered in worldwide literature. In Brazil, only one report of gynandromorphism was observed in a specimen of Lutzomyia longipalpis (Lutz & Neiva 1912) from the state of the Ceará. We report here on the first known case of gynandromorphism in Lutzomyia davisi (Root 1934) captured in Alta Floresta, Mato Grosso state, Brazil.