Adams, the former IRA boss in Belfast at the time of Mrs McConville’s murder in 1972, presented himself to detectives at the serious crime suite in Antrim around 7 pm on Wednesday night.
The 65-year-old went voluntarily with his solicitor by prior arrangement to meet with the PSNI’s Terrorist Investigation Unit.
However, on arrival he was formally arrested and cautioned.
He can be held for up to 48 hours before either being released or charge.
However, the PSNI can apply to a court for an extension to his detention to carry out further questioning.
He was being quizzed by senior detectives from the TIU over the mother-of-ten’s murder four decades ago.
Questioning will resume this morning at the anti-terror suite.
Adams was arrested under Section 41 of the Terrorism Act and can be held for up to 48 hours before being charged or released.
The Louth TD has always denied involvement in the killing. He has also denied ever being a member of the IRA.
Before handing himself in, Adams said: “While I have concerns about the timing, I am voluntarily meeting with the PSNI this evening.”
His former Adjutant Ivor Bell was recently charged in connection with the mother’s murder and abduction.
Bell was remanded in custody but later released on High Court bail.
Adams recently asked his solicitor to write to the PSNI to ask detectives if they wished to interview him about the murder.
In recorded interviews for the Boston Tapes, former IRA man and close pal of the Sinn Fein president, Brendan Hughes, said that Adams had given the order for Mrs McConville’s abduction and murder.
A number of women have also been arrested in recent weeks in connection with Mrs McConville’s murder.
Her family have welcome Adams’ arrest saying that “at last the PSNI investigation is moving in the right direction. We just want justice for our mother.”
Mrs McConville was aged 37 when she was abducted from her Divis Flats home off the Falls Road in 1972.
Next week she would be 80 if she was still alive.