The carpenter worm, Chilecomadia valdiviana (Lepidoptera: Cossidae), is a polyphagous insect native to Chile that is associated with trees and bushes, including economically important species such as eucalyptus, avocado, and apples. We used a Y-olfactometer to analyze the olfactory responses of larvae to conspecific larvae, hexane extracts of larvae, and synthetic samples of the major components present in the extract (i.e., (Z)-5,13-tetradecadienyl acetate, (Z)-5-tetradecenyl acetate, and dodecyl acetate). The results obtained provide empirical evidence that (Z)-5,13-tetradecadienyl acetate is used as an aggregation pheromone by the larvae. The results are discussed in view of the existing information.