Discrimination between conspecifics is important in mediating social interactions between several individuals in a network environment. In great tits, Parus major, females readily distinguish between the songs of their mate and those of a stranger. The high degree of song sharing among neighbouring males, however, raises the question of whether females are also able to perceive differences between songs shared by their mate and a neighbour. The great tit is a socially monogamous, hole-nesting species with biparental care. Pair bond maintenance and coordination of the pair's reproductive efforts are important, and the female's ability to recognize her mate's song should therefore be adaptive. In a neighbour-mate discrimination playback experiment, we presented 13 incubating great tit females situated inside nestboxes with a song of their mate and the same song type from a neighbour. Each female was tested in two trials with the opposite order of stimulus presentation. Eleven females responded to the song of their mate in both trials, while two females responded to those of their mate in one trial and a neighbour in the other. Thus, great tit females are able to perceive subtle individual differences between their mate's song and a neighbour's rendition of the same song type despite being inside nestboxes, which are known to alter the received song structure and intensity. We suggest that this female discrimination ability inside nest holes is mediated by a high perceptual sensitivity towards small variations in song structure that should be adaptive to this hole-nesting bird species.