Although offspring delay dispersal past the age of independence in many Thryothorus species, cooperative breeding has not been recorded in this genus. Here, I present the first observation of cooperative breeding in a Thryothorus wren (Buff-breasted Wren, T. leucotis). Of 41 offspring that delayed dispersal past the age of independence, 4 individuals stayed on their natal territory until their parent's next breeding attempt, indicating a low potential for cooperative breeding. Of these four individuals, one male provisioned 11- to 15-day-old nestlings and one female approached her parents' nest but was repeatedly driven away from it by her father. The retained female was apparently tolerated when in the vicinity of fledglings, but feeding was never positively confirmed.