A total of 38 species of mosquitoes of the Culicidae family of two subfamilies Anophelinae and Culicinae belonging to 6 genera, were identified on the territory of Kharkiv Region from 2009 to 2019. Dirofilaria larvae were found in 932 insects, which was 4.46 % of the surveyed mosquitoes. The prevalence of the infection of female mosquitoes by dirofilaria was 4.46 ± 0.24 %, while the mean intensity of dirofilariae was 5.4 ± 2.1. Infection of mosquitoes with dirofilariae is currently detected in 11 districts of Kharkiv Region and the city of Kharkiv. The infection rate of mosquitoes of the genus Aedes was 3.83 ± 0.63 %, of the genus Culex — 0.75 ± 0.34 %, of the genus Anopheles — 0.12 ± 0.39 %, whereas females of the genera Culiseta, Coquillettidia, and Uranotaenia were uninfected. It was found that in Kharkiv Region there were 2 types of canine dirofilariae — Dirofilaria immitis (Leidy, 1856) and Dirofilaria repens (Railliet & Henry, 1911), with a predominance of Dirofilaria repens. For the period from 2009 to 2019, we examined 378 blood samples from dogs (190 males and 188 females) aged from 8 months to 13 years with suspected dirofilariasis. According to the results of the studies, 140 samples were positive, the prevalence of infection by the larvae of Dirofilaria spp. in blood samples from dogs with suspected dirofilariasis was 37.03 ± 0.12 %, while infection with Dirofilaria immitis was 2.86 ± 0.45 %, and Dirofilaria repens — 97.35 ± 0.24 %. The number of positive samples from mongrel dogs was 42 (30 %). It was found that cats are more often amicrofilariaemic than dogs.