AbstractOne new genus with a new species assigned to the subfamily Mesohelorinae in the Heloridae, Archaeohelorus hoi, gen. et sp. nov., and two new genera with four new species assigned to the subfamily Mesoserphinae in the Mesoserphidae—Sinoserphus wui gen. et sp. nov.; Sinoserphus shihae, sp. nov.; Sinoserphus lillianae, sp. nov.; and Yanliaoserphus jurassicus, gen. et sp. nov.—are described from the Middle Jurassic Jiulongshan Formation of Inner Mongolia, China. Here, we document the earliest fossil records hitherto of helorid and mesoserphid wasps, extending their existence to the Middle Jurassic. It is proposed that Heloridae and Mesoserphidae might have originated from northeastern China. Morphological changes of their antennae, wing venation, and metasoma based on current knowledge are discussed.