We present the first record of the weakly electric fish Gymnotus henni in Panama, which also represents the first record of Gymnotus in the Pacific slope of the country. One specimen was collected in a tributary of the Chucunaque River in the Tuira basin. The species showed a monophasic electric organ discharge. Molecular analyses indicated that G. henni from Panama and Colombia are closely related and represent an independent and basal lineage to the Central American G. cylindricus and South American G. carapo groups. Evolutionary and biogeographic implications are discussed.