Monophyly of the superfamily Dioctophymatoidea was assessed based on analyses of DNA sequence variation among 3 of 4 constituent genera (5 species). Represented is the first molecular phylogenetic evaluation of the Dioctophymatoidea using maximum parsimony, maximum likelihood, and Bayesian inference of 18S nuclear DNA (786 base-pair [bp] segment) and mitochondrial cytochrome oxidase 1 (293 bp) genes. Dioctophymatoidea is monophyletic and includes a clade with Dioctophyme renale and Eustrongylides ignotus (Dioctophymatidae) as the sister of Soboliphyme baturini, Soboliphyme jamesoni, and Soboliphyme abei (Soboliphymatidae). Within Soboliphymatidae, S. baturini is the sister of S. jamesoni and S. abei.