I investigated the physiognomic and floristic characteristics of Swainson's Warbler (Limnothlypis swainsonii) territories at five localities within its core breeding range in Arkansas, Mississippi, Louisiana, and Florida. The warbler attained its greatest abundance (10–20 territorial males/km²) in floodplain forest characterized by small (<25 cm dbh) trees (ca 620–820 stems/ha) and understory thickets of saplings, vines, and shrubs (ca 35,000–48,000 small woody stems/ha). Territories in mature forest typically were associated with disturbance gaps. Canopy height, basal area, and floristics appear to be relatively unimportant factors in habitat selection, provided that understory requirements are met, which explains the warbler's occurrence in regenerating clearcuts as well as in relic tracts of old growth forest. Giant cane (Arundinaria gigantea), hypothesized to be an essential habitat requisite along the northern periphery of its breeding range, was sparse or absent in the prime breeding locations surveyed in this study. Selective thinning and clearcutting are viable habitat management techniques for the Swainson's Warbler.