Ornithomimidae was first defined by Sereno (1998) as a stem-based clade to circumscribe all commonly known genera, from Pelecanimimis to Ornithomimus. This taxonomic content corresponded with older usage and that of Galton and Smith (1990), when a family level taxon was used to circumscribe known genera. Earlier, Barsbold (1976) proposed a redundant taxon, Ornithomimosauria, to recognise the anatomical distinctiveness of the group, and eventually the name was adopted by most workers for the clade, with Ornithomimidae as one of three included families (Osmólska 1997).

Sereno (1998:65) defined Ornithomimidae as a stem-based taxon to include all of the genera, but mistakenly listed the therizinosaurid Erlikosaurus as an external specifier rather than an alvarezsaurid or suite of external specifiers. Here the family is defined to match current usage, which restricts the taxon to a subset of the clade (e.g. Osmólska 1997; Kobayashi and Lü 2003, Makovicky et al. 2004). The active definition is a first-order revision of the definition proposed by Sereno (1998), which uses several basal ornithomimosaurs as external specifiers.