Males of Calopteryx splendens use two alternative mating tactics, territoriality, and non-territoriality. These different mating tactics are shown to vary between males within the same population and previous studies have shown that territorial males have considerably higher fitness than non-territorial males. In this paper, we tested whether the wing spot size as sexual ornament, wing length, relative wing spot size, asymmetry in wing length, asymmetry in wing spot size, or asymmetry in relative wing spot size differed between the territorial and non-territorial males. We sampled C. splendens males, representing both mating tactics, from a river system in south-west Finland. According to our results, territorial males have larger wing spot than non-territorial males. In contrast, there were no differences in the other tested traits between the territorial and non-territorial males. In conclusion, our data show that the size of pigmented wing spots may predict the alternative mating tactic of C. splendens males.