The diversity of praeaulacid wasps in Kachin amber is relatively poorly documented. Here, a new genus and species of praeaulacid wasp are described and illustrated from the mid-Cretaceous Kachin amber as Archeogastrinus kachinensis gen. et sp. nov., and placed in the subfamily Praeaulacinae. This new genus is distinguishable from the other Praeaulacidae because of its particular tibial spurs formula 1-2-2; its forewings with a long and thin pterostigma, a 1-M longer than 1-Rs, a 1-Rs longer than its distance to pterostigma, a crossvein 2r-rs aligned (or nearly) with 2rs-m and originating near the middle of pterostigma, a 2rs-m present, a cell 3rm long, a 1cu-a postfurcal to 1-M, a vein 2-M distinct; its hind wings cu-a reaching Cu distad M + Cu fork; and its metasoma with a first segment petiole-like (i.e., long and thin) and ventrally inflated in its distal half. The position of the genus Mesevania is briefly discussed, as well as the validity of the genus Paleosyncrasis, both described from the mid-Cretaceous Kachin amber.