Aruba, Bahamas, Belize, Canada (B), Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Mexico, Netherlands Antilles, Nicaragua, Panama, Puerto Rico, St Pierre and Miquelon (B) (P), Turks and Caicos Islands, USA (B), Venezuela.
Breeds in central-western and southern Canada (south-eastern Yukon and eastern British Columbia east to Newfoundland and Nova Scotia) and in north-eastern USA south to northern Illinois, northern Ohio, northern New England and, in Appalachians, to West Virginia. Migrates to Central America (southern from southern Nicaragua) and north-western South America.
 
Population
Estimated population is 7,000,000 (2010).
Mourning Warbler (Geothlypis philadelphia) [XC830465]
by Sue Riffe from Dynasty Coffe Gutierrez, Bilbao, Planadas, Tolima, Colombia (call)
Mourning Warbler (Geothlypis philadelphia) [XC419819]
by Sue Riffe from Au Sable SF - Big Creek Rd, Michigan, United States (song)
Subspecies
No subspecies.
Genus sometimes subsumed in Geothlypis. Forms a species pair with MacGillivray's Warbler (Geothlypis tolmiei), the two probably constituting a superspecies. Ranges overlap in western Canada (Peace Region of British Columbia). Claimed hybrids from this zone have been considered variants of Mourning Warbler (Geothlypis philadelphia) with white eye-crescents (such variants occur throughout this species' range), but recent analysis combining molecular and morphological data sets confirms numerous hybrid individuals with mixed characters, including 18 of 50 birds genotyped (36%) showing both western and eastern alleles. Also known to have hybridized with Common Yellowthroat (Geothlypis trichas), Canada Warbler (Cardellina canadensis) and Kentucky Warbler (Geothlypis formosa). Reported hybrid with Connecticut Warbler (Oporornis agilis) generally thought to have been aberrant individual of Mourning Warbler (Geothlypis philadelphia). Reported hybrid with Blue-winged Warbler (Vermivora cyanoptera) now considered to have involved interbreeding of Blue-winged Warbler (Vermivora cyanoptera) with Kentucky Warbler (Geothlypis formosa).