This study of mosquitoes in Lika, geographically, geologically and climatically a very specific region, was conducted to gain insight into the composition and relative abundance of the mosquito fauna, as well as to check for the possible presence of invasive species. Sampling took place from July to September 2020. Mosquito larvae were captured from medium and small breeding sites using a 25 cm diameter net and a plastic dipper. Adult specimens were sampled in both urban and rural areas using CO2 baited CDC traps, CO2 baited BG Sentinel traps with BG Lure and human landing catch. The study was conducted at 69 sites. We collected 5,126 specimens (100 adults and 5,026 larvae) and demonstrated the presence of 16 mosquito species. CDC traps were almost five times more effective (quantity and quality) than BG Sentinel traps. The most common mosquito taxa caught in Lika were Culex pipiens complex (78.36% of all larvae) and Ae. geniculatus (30.26% of all adults). Both invasive mosquito species present in Croatia, Aedes albopictus and Ae. japonicus, were recorded, with Ae. albopictus being detected in Lika for the first time. Aedes japonicus was widespread, recorded in 23 localities. According to molecular analysis, only An. maculipennis s.s. was confirmed in the An. maculipennis complex. Within the Cx. pipiens complex, both Cx. pipiens biotypes, pipiens and molestus were confirmed together with one single hybrid specimen. Analysis of mosquito occurrence with regard to altitude shows that most samples and species were collected between 601 and 700 m a.s.l., although the Shannon evenness index and Hill’s index show the highest value in the range of 901 to 1140 m a.s.l. In this systematic study on the mosquito fauna in Lika, a significant species diversity, including invasive species, was found.