The train of the peacock (Pavo cristatus) is one of the most complex color ornaments among bird species. It is composed of feathers ending in a colorful iridescent eyespot. Darwin was the first to suggest that the iridescent coloration of the eyespot had evolved through female mate choice. However, the evidence was lacking until today. To investigate this issue, we collected eyespots from 22 peacocks and observed female visits and mate choice. We used a novel approach to assess the coloration of the eyespots. We analyzed the eyespots’ optical properties from the point of view of a receiver placed in front of the peacock and we measured the iridescence due to the change in coloration resulting from viewing the feather from different angles. We also took the peahen visual abilities into account to obtain a reliable representation of the peahen’s vision. We found that females potentially use the iridescence of the eyespots to detect males at longer distance and to choose to visit them. Furthermore, they may use the brightness of the eyespots and the iridescence at shorter range to assess potential mates. We provide the first evidence that the iridescent coloration of the eyespot has the potential to affect mating decisions in the peafowl.