West Nile virus is a typical mosquito-borne flavivirus, and it is transmitted between mosquitoes and birds in nature. As an incidental host, humans are susceptible to WNV infection. WNV infection in humans can result in fever, meningitis, and encephalitis. Approved human vaccines or therapies are not available for WNV infection. In this chapter, we focus on the techniques for WNV infection and detection in mosquitoes. The technical details include: (1) WNV infection in cell culture; (2) Mosquito rearing; (3) WNV infection in mosquitoes via thoracic microinjection; (4) Detection of WNV infection in mosquitoes; (5) Determination of WNV M.I.D50 in mosquitoes; (6) WNV infection in mosquitoes via membrane blood feeding; (7) WNV infection via blood feeding on mice; (8) Immunofluorescence staining of WNV infected mosquito tissues.