In a written statement, Adams, 65, said he was meeting with police "voluntarily." In a posting on Twitter, however, the Police Service of Northern Ireland stated that it had arrested an unnamed, 65-year-old man in connection with the unsolved investigation.
McConville's killing, labeled by some as a war crime, remains one of the more grisly episodes of Northern Ireland's "troubles." She was kidnapped at gunpoint in front of her children and later executed.
In 1999, the IRA admitted it had murdered McConville. Her body wasn't found until 2003, buried on a beach in the Republic of Ireland.
New leads in the case have come recently from oral history recordings made by researchers at Boston College. The interviews with former Northern Ireland paramilitaries were to be kept secret until after those involved had died. But a long legal battle in the U.S. forced Boston College to hand over some of the material.
Statements on those recordings led to charges last month against former IRA leader Ivor Bell, 77, in connection with McConville's murder.
Former IRA members have alleged that Adams, as a key leader in the organization, ordered the killing. Adams has continually denied IRA membership and involvement in the case.
"Malicious allegations have been made against me. I reject these," Adams said Wednesday. "I believe that the killing of Jean McConville and the secret burial of her body was wrong and a grievous injustice to her and her family."
Adams' arrest comes as Northern Ireland grapples with the grim legacy of the "troubles." Thousands of homicides over 30 years of conflict remain unsolved.
Disagreement over how to address those cases is one reason why talks between republican and unionist parties in Northern Ireland broke down this year. Those negotiations, brokered by the U.S. special envoy to Northern Ireland, Richard Haas, aim at resolving issues left over from the peace process that led to the Good Friday agreement in 1998.
Some officials in Northern Ireland have called for prosecutions to be replaced with a truth and reconciliation process that might provide a level of amnesty in exchange for information that could help families determine what happened to their loved ones.
In a statement, Sinn Fein denounced Adams' arrest.
"I believe the timing of this latest decision by the [Police Service of Northern Ireland] is politically motivated and designed to damage Gerry Adams and Sinn Fein," said the party's deputy leader, Mary Lou McDonald. "It is Sinn Fein's view that legacy issues and dealing with the past, including past conflict events, are best addressed through an independent, international, truth recovery process."
The arrest comes just weeks after former IRA member and current Deputy First Minister of Northern Ireland Martin McGuinness attended a state banquet at Windsor Castle in England. The event was seen as a watershed moment for Britain and Northern Ireland. McGuinness toasted