Aim: The aim of this cross-sectional study was to compare the age-related declines in swimming, cycling, and running and overall race times between males and females in an Olympic distance triathlon, the 'Zürich Triathlon' in Switzerland. Methods: Swimming (1.5 km), cycling (40 km), running (10 km) and overall race times of 7939 total finishers (1666 females and 6273 males) from 2000 to 2010 in the "Zürich Triathlon" were analysed. Results: There was a significant (P<0.001) age effect on performance for both males and females independently of the discipline. No significant difference in the overall race time was observed between 18 and 34 years for both genders. There was an interaction (P<0.001) of age and gender for swimming, cycling and overall race times, but not for running times. The age-related declines in performance were significantly less pronounced for males compared with females for swimming (>50 years), for cycling (>40 years) and for overall race time (>40 years). Conclusion: These data suggest that the age and gender interactions in an Olympic distance triathlon performance differ between the three locomotion modes. Further studies investigating training regimes, competition experience or socio-demographic factors are needed to get a better insight in the phenomenon of the gender specific age-related declines in endurance performance.