Police are appealing for witnesses after allegations emerged that a youth support worker sexually abused a teenager in Canberra more than two decades ago.

Police say the alleged offending occurred between 2002 and 2003 and involved a man working as a community service worker with the Ted Noffs Foundation in Watson.

Investigators have received information that the man allegedly committed sexual offences against a teenager during that period.

Police are urging anyone with information about the man or the alleged offending to come forward, regardless of how much time has passed.

Specialist sexual assault investigators are available to guide victims through the investigative process, with additional support available through agencies including Victim Support ACT and the Canberra Rape Crisis Centre.

Anyone who can assist is urged to contact police on 1800 333000 or via the Crime Stoppers ACT website.