Gynandromorphs of Culex nigripalpus Theobald (2), Cx. pedroi Sirivanakarn and Belkin (1) and Aedes albopictus (Skuse) (2) are described. Two individuals of the latter species were reared in the laboratory, while the remaining three specimens were wild-caught with different traps in rural areas in Valle del Cauca department, southwestern Colombia. All of the individuals were mounted on microscopic slides with Canada balsam. From each mosquito, main morphological characteristics are described and illustrated. Due to the paucity of information about this subject, these findings as well as other relevant cases are discussed.