We investigated whether mitochondrial (mtDNA) haplogroups and maternal family history of diabetes mellitus were associated with vascular diabetes mellitus complications in a population-based cohort of 299 Finnish diabetes mellitus patients with disease onset in young adult age. We found that haplogroup U was more prevalent among patients with no vascular diabetes mellitus complications than among those with at least one complication (p = 0.038). Haplogroup U was also more prevalent among the patients who reported maternal family history of diabetes mellitus than among those who did not (p = 0.0013). Furthermore, haplogroup U was more prevalent among patients with maternal family history of diabetes mellitus but no vascular diabetes mellitus complications than among those with at least one vascular diabetes mellitus complication but no maternal family history of diabetes mellitus (p = 0.0003 for difference). These findings suggest that different mtDNA-related factors may influence the risk of diabetes mellitus per se and the risk of vascular diabetes mellitus complications. Further studies are, however, warranted to replicate and elaborate on these results.