Nasonia courtship behaviour includes easily quantifiable, stereotyped components. We analysed displays of N. vitripennis x N. longicornis hybrid males. Most of them performed well-organised displays that were intermediate between the parental species. However, in both reciprocal crosses, a significant bias towards the behaviour of the grandpaternal species was observed. Possible explanations for this effect are a biased recovery of genotypes, either due to nucleo-cytoplasmic interaction or non-mendelian transmission, or differential activation of genes in hybrid females. This study is a first step towards unravelling the genetic architecture of courtship behaviour of Nasonia, which may provide information about factors responsible for species isolation.