It consists of an articulated but fragmentary skull and lower jaws comprehending paired maxillae, a partial jugal, palate bones and dentaries.

The body length was estimated at fifty to sixty centimetres,[3] making the Archaiornithoides type one of the smallest known non-avian dinosaurs.

This conclusion rested on key bird-like features; an interdigitated suture between the premaxilla and maxilla, broad palatal shelves, pneumatic sinuses, lack of interdental plates, and unserrated teeth.

Some scientists had suggested that the juvenile specimen of Archaeornithoides may belong to a previously known species of Mongolian troodontid, either Saurornithoides or Byronosaurus.

[5] Elzanowski and Wellnhofer noted that the specimen has distinct bite marks while the back of the head fragment was ragged, and suggested that the jaws were bitten off from its braincase by a Deltatheridium mammal the size of a weasel (adding that these are common in the Bayn Dzak assemblage).