Models of sexual selection suggest that females should prefer to mate with older males because old age is evidence of heritable high viability. In a longitudinal analysis, we demonstrate that male field crickets (Gryllus campestris) alter their calling song with age. Carrier frequency, a calling song character related to growing condition and the main song component under female preference, changed towards higher sexual attractiveness with age. Body mass decreased slightly with age, while chirp rate, an indicator of current condition, remained stable. By choosing males singing at a low frequency, female field crickets would base their mate choice decision on a sexual trait that indicates superior growing conditions as juvenile and on viability, i.e. enhanced current condition as adult.