To evaluate the reproductive potential of female and male gametes in a haploid plant derived from seedlings of ‘Banpeiyu’ pummelo, we performed crosses between the haploid and several diploid citrus cultivars. In the crosses with the diploid cultivars as pollen parents, no fruit set on the haploid in all cross combinations. However, developed seeds were obtained in four cross combinations, when some monoembryonic diploid cultivars were pollinated with pollen of the haploid. These seeds germinated normally and developed into diploid, vigorous seedlings with large wing leaves, typical of ‘Banpeiyu’ pummelo. Furthermore, the hybridity of a seedling obtained from the cross between ‘Kiyomi’ tangor and the haploid was confirmed by random amplified polymorphic DNA (RAPD) analysis and chromosome composition by chromomycin A₃ (CMA) staining. These results suggest that the haploid produced fertile pollen grains (n=9).