[1] Culex nigripalpus has been found to occur in the following countries: Anguilla, Bahamas, Barbados, Belize, Brazil, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, El Salvador, French Guiana, Grenada, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Montserrat, Nicaragua, Panama, Paraguay, Peru, Puerto Rico, Saint Lucia, Saint Vincent and the Grenadines, Suriname, Trinidad and Tobago, United States, Venezuela, Virgin Islands.

[2] In the United States, it is found from Texas to North Carolina in warm, humid coastal habitats and in the Mississippi River basin as far north as Kentucky.

[1] Culex nigripalpus larvae live in fresh water in semi-permanent or permanent marshes, ditches, retention ponds, and grassy pools, and females prefer to lay eggs in freshly flooded ditches.

[1][4] It has been experimentally demonstrated to be capable of transmitting West Nile virus (WNV).

It is also a vector of transmission of Eastern equine encephalitis (EEE), dog heartworm, and Avian malaria.