A self-proclaimed Adelaide "pedophile hunter" has staged a dramatic citizen's arrest of a man he has accused of being a child predator.

The man – who has asked not to be identified – claims to have sent the alleged predator a photo of a teenage boy via an adult hook-up website.

He told 9NEWS he “played a little dumb” regarding the legal age of consent during the interaction with the alleged predator.

The accused predator was filmed by the vigilante during the 'arrest'. (9NEWS)

The vigilante says the predator "played a little dumb". (9NEWS)

“He said ‘17’ and I made it clear to him three times after that that I am definitely underneath that (age),” the man said.

He then arranged to meet at a train station in Adelaide's inner-southern suburb.

“You're not going anywhere,” he can be heard telling the man during the arrest, which he filmed and posted to YouTube.

The vigilante 'arrested' the accused pedophile before police arrived. (9NEWS)

“The cops are on their way. I will stand over there.

“You'll stay right where I tell you to stay.”

The alleged predator was subsequently arrested by police. Computers were also reportedly seized from his nearby home.

The vigilante has taken the law into his own hands. (9NEWS)

Police however said the man has not been charged and the investigation is ongoing.

They have advised anyone considering similar vigilante behaviour to “let us do our job”.

"Don't take the law into your own hands in relation to any criminal matter,” they said in a statement.

Police arrested the accused predator and seized his computer and other items. (9NEWS)

The hunter insists however he was not trying to “mete out my own justice”.