Current research on behavioural consistency showed that various types of animal behaviour are highly repeatable in the context of mate choice, exploration and parental care, including nest protection. However, the repeatability of aggressive nest defence has not yet been studied in hosts of brood parasites, although host aggression against adult parasites represents a crucial line of antiparasitic defences. Here, we investigated the between-season repeatability of the great reed warbler (Acrocephalus arundinaceus) aggression towards a stuffed dummy of the brood parasitic common cuckoo (Cuculus canorus). We found that under the relatively stable risk of brood parasitism across breeding seasons, female responses to the cuckoo were highly repeatable, whereas male responses were variable. We suggest that the potential explanation for the observed patterns of female and male behaviours may lie in female's prominent roles in offspring care and nest protection, and in her lower renesting potential in comparison with that of males. However, further studies on the relationship between host aggression and other types of behaviours (host personality) and their fitness consequences under the fluctuating parasitism pressures are required to clarify the adaptive significance of aggressive behaviour observed in hosts of brood parasites.