Protecting the Innocent approached the man on his doorstep in Leeds recently.
They live streamed the confrontation on social media and police were subsequently informed.
The group's Facebook page has over 26,000 followers.
However, they have now admitted the 'sting' was a mistake and that the victim was not the same man whom they had been pursuing.
They posted a statement on their Facebook page, which is open to the public.
"Mr ______ was pending police investigation after our sting. As we further investigated ourselves we discovered in fact we had stung the wrong person. Mr ______ who was shown on camera is NOT the man contacting us and other decoys as we suspected. We are now in process of contacting the police, his family and all other known associated people that came forward to clear this man's name.
"From all of us at Protecting the Innocent - if we can assist in any way please do not hesitate to contact us. No amount of apologies will fix what has happened and we cannot turn back time. However we will continue to clear your name.
"We profusely apologise for all inconvenience and distress caused during this time, and if we can assist you in any way please let us know and we will work with you to right this horrible wrong."
West Yorkshire Police have in the past raised concerns about the activities of vigilante groups, whose actions can often jeopardise court cases. A statement from the force read:
"We would always encourage members of the public to report any illegal activity relating to child sexual exploitation which they come across online.
"While the force does of course share concerns regarding the internet activity of potential child abusers and the danger they present, it must be stressed that the activity that ‘paedophile hunter’ related groups seek to engage in, is the responsibility of law enforcement agencies.
"West Yorkshire Police fully investigates all allegations of child sexual exploitation and has dedicated, specialist safeguarding officers in all our policing districts.
We urge members of such 'exposure' groups not to carry out this activity and instead to report suspected offences in West Yorkshire to the force via 101 or the independent Crimestoppers charity on 0800 555 111."
Reports can also be made online to CEOP at https://ceop.police.uk/safety-centre/