Mosquitoes, which are in the Culicidae family and have blood-sucking properties, infect humans and animals with many diseases. In the present study, it was aimed that mosquitoes spreading in the Kocaeli province were detected species identification based on DNA barcoding method. DNA isolation was performed with the samples of mosquitoes collected in the Kocaeli province between June 2017 and September 2018. Then, Polymerase Chain Reaction (PCR) and DNA sequence analysis were applied by using universal primers of the mitochondrial COI gene. The sequences in FASTA format obtained with the Chromas program were compared with those of other mosquito species in the world through the NCBI-BLAST database. For phylogenetic analysis, the sequences were uploaded into the MEGA X program, and phylogenetic trees were created in the Maximum Likelihood method, Tamura-Nei Model (Tamura & Nei, 1993), Bootstrap 1000. Among mosquitoes collected in this study, 7 species belonging to Aedes, Anopheles, Culiseta and Culex genera were identified and characterized as Aedes geniculatus (n = 10), Aedes albopictus (n = 7), Anopheles funestus (n = 1), Anopheles plumbeus (n = 1), Culiseta longiareolata (n = 1), Cx. torrentium (n = 1) and Cx. pipiens complex sp. (n = 33).Within them, Cx. pipiens complex sp. was found as the dominant species in Kocaeli. In conclusion, this study revealed the first molecular research of mosquito species spreading in Kocaeli and provided records to GenBank.