We report on the discovery of a distinct female song in Nava's Wren (Hylorchilus navai), similar to that recently discovered in Sumichrast's Wren (Hylorchilus sumichrasti). In both species, females sometimes countersing with males but do not combine their songs into a synchronized duet as in many other tropical wrens. We provide observations that suggest territorial defense, intra-pair contact, and perhaps mate-guarding as possible functions of female song in Hylorchilus, a little-known genus endemic to Mexico.