An addendum to the recent checklist of the Chrysididae from Mongolia is given. Examination of old museum material and recently collected specimens has led to the discovery of eight new records for the country and eleven new species for science. Eight species are newly recorded from Mongolia: Chrysis inclinata Linsenmaier, 1959, C. martinella du Buysson, 1900, C. speciosa Radoszkowski, 1877, Euchroeus purpuratus (Fabricius, 1787), Holopyga lucida (Lepeletier, 1806), H. similis Mocsáry, 1889, Hedychridium femoratum (Dahlbom, 1854) and H. leleji Rosa, 2017. Two species, Hedychridium cupreum (Dahlbom, 1845) and H. propodeale Rosa, 2017 are excluded from the checklist of Mongolian Chrysididae: the former is described here as H. erythrosomasp. nov., the latter is identified as H. leleji Rosa, 2017. The hitherto unknown male of Chrysis mocsaryi Radoszkowski, 1889 is described and illustrated. Eleven new species are described: Chrysis strakaisp. nov., C. woodisp. nov., Hedychridium erythrosomasp. nov., H. frontalesp. nov., H. jacobsisp. nov., H. splendenssp. nov., H. striatumsp. nov., H. varvaraesp. nov., H. weiisp. nov., Holopyga tyrnerisp. nov., and Philoctetes borekisp. nov. Keys to males and females of all known Mongolian species of Hedychridium Abeille de Perrin, 1878 are provided. The Mongolian cuckoo wasp fauna now comprises 107 species in 18 genera and two subfamilies.