Hydatidiform moles are gestational diseases with abnormal development of the villous trophoblast and characterized by an excess of paternal to maternal genetic material. Complete moles are usually diploid and androgenetic, and are thought to develop after the fertilization of an "empty ovum" by either a haploid spermatozoon or two spermatozoa. We report a case of a complete mole in which fluorescence in situ hybridization (FISH) incidentally disclosed trisomy 13. Microsatellite genotyping showed a single allele at each of the markers tested on the chorionic villi, and comparison with parental peripheral blood specimens revealed that the markers were all of paternal origin. These results confirmed the paternal origin of all three copies of chromosome 13, and the isodisomy for each chromosome was consistent with duplication of a monospermic fertilization event and subsequent non-disjunction. To the best of our knowledge, this is the only case of an androgenetic complete mole with trisomy 13 described in the scientific literature. We present a review of the literature and hypothesize that the trisomy 13 in our case likely resulted from non-disjunction of chromosome 13.