An analysis of the phylogeny of Ascidae sensu lato and related groups based on DNA data is presented. This group was recently separated in Ascidae sensu stricto, Melicharidae and Blattisociidae, retaining the first two families in Ascoidea and moving the third to Phytoseioidea. These changes were made based mainly on the morphology of the spermathecal apparatus. On the other hand, considerable morphological similarities exist between some genera of Ascidae s.l. and of Phytoseiidae and Rhodacaridae. This study uses partial sequences from the 18S and 28S regions of the nuclear ribosomal DNA to infer the phylogenetic relationships between Ascidae s.s., Melicharidae and Blattisociidae as well as their relationships with Phytoseiidae and Rhodacaridae. Results obtained with the Bayesian and Maximum Likelihood methods supported the paraphyly of Ascidae s.l., but did not support the recent assignment of their members into the recently conformed superfamilies. The results also suggested that Blattisociidae and Phytoseiidae constitute a monophyletic group and that Rhodacaridae is paraphyletic. Except for Protogamasellopsis posnaniensis Wiśniewski and Hirschmann, all rhodacaroid representatives considered in this analysis (Digamasellidae, Ologamasidae and Rhodacaridae), as well as Zygoseius Berlese (a genus currently of uncertain familial placement), were placed at the base of the constructed phylogenetic tree, constituting a sister group of the previously mentioned taxa. The phylogenetic hypothesis presented here suggests the need to reconsider the morphological structures presently used to characterize the families of Ascoidea, Phytoseioidea and Rhodacaroidea.