Jeholosaurus shangyuanensis is a small ornithischian dinosaur from the Lower Cretaceous Yixian Formation of the Lujiatun locality, Liaoning Province, China. Here, we provide the first detailed description of its postcranial skeleton based on the holotype and four other well-preserved skeletons, and compare it with material of other primitive cerapodans. Jeholosaurus can be diagnosed on the basis of one postcranial autapomorphy, relating to the absence of parapophyses from the anterior dorsal vertebrae, and a unique combination of postcranial characters, but its anatomy is otherwise similar to that of many other basal ornithischians. A phylogenetic analysis incorporating these new postcranial data confirms previous suggestions that Jeholosaurus is a basal ornithopod and that it forms a clade with Changchunsaurus and Haya; Koreanosaurus and Yueosaurus might also belong to this clade, though additional material of both will be required to test this hypothesis. The name Jeholosauridae is proposed for this apparently endemic group of Cretaceous East Asian taxa.