The new gregarious parasitoid Meteorus acerbiavorus sp. nov. (Hymenoptera, Braconidae) was reared from the cocoons of Acerbia alpina (Quensel) (Lepidoptera, Arctiidae) in north-western Finnish Lapland. This species belongs to Meteorus rubens (Nees) species group and differs from the most related M. rubens in the following features: the eyes densely setose; the median lobe of the mesoscutum, scutellum, mesopleuron, and the hind coxa entirely or at least partly rugulose-granulate or rugose-areolate and sometimes with granulation; the ovipositor subapically with distinct dorsal node; the ventral borders of the first metasomal tergum weakly separated by narrow space in its basal half; the colour of the body and legs mostly or entirely dark; the fore wing more or less darkened. Phylogenetic relationships among several Meteorus species close to M. rubens including new M. acerbiavorus were investigated based on DNA sequence fragments of the mitochondrial COI and the nuclear 28S rDNA genes. The discussions on the species groups of Meteorus, on distribution of Acerbia alpina in the Holarctic and on its known parasitoids are presented.