Mr Adams has been held in custody at Antrim Serious Crime Suite since Wednesday evening when he was arrested after presenting himself at the PSNI station.
Police had until 8pm on Friday to question the 65-year-old however, following a court bid, they have now received a further 48 hours with the Louth TD.
A statement from the PSNI said: "Detectives investigating the abduction and murder of Jean McConville have been granted an extra 48 hours to interview a 65-year-old man."
The former West Belfast MP has been held under the Terrorism Act in relation to the 1972 abduction and murder of Jean McConville.
This is political policing at its most blatant.
The 37-year-old was interrogated, shot in the back of the head and then secretly buried - so becoming one of the "Disappeared" victims of the Troubles.
Her body was not found until 2003 on a beach in Co Louth, 50 miles from her home.
Reacting to the news that police had been given more time, Gerry Kelly MLA described his party leader's continued detention as "blatant political policing".
He went on: "The arrest and continued detention of Gerry Adams is deliberately timed to coincide with the elections in three weeks' time.
"Sinn Féin will not be intimidated by the action of a small cabal in the PSNI who are opposed to the peace process and political change."
Claims that the arrest was "politically motivated" have been rejected by Prime Minister David Cameron, First Minister Peter Robinson of the DUP and Alliance Justice Minister David Ford.
Earlier, deputy First Minister Martin McGuinness said Sinn Féin would "reflect" and "review" its support for policing if Mr Adams is charged. However, he urged republicans to remain calm.
He said: "There are many progressive and open-minded elements in the new policing arrangements who are wedded to accountable and impartial policing.
"But there is a small cabal in the PSNI who have a different agenda - a negative and destructive agenda to both the peace process and to Sinn Féin.
"Yesterday, I said that the timing of the arrest of Gerry Adams was politically motivated. Today's decision by the PSNI to seek an extension confirms my view."
Mrs McConville, a 37-year-old widow and mother of 10 children, was abducted in December 1972 from her flat in the Divis area of the city and shot by the IRA.
She was one of the so-called 'Disappeared' and her body was recovered on a beach in Co Louth in August 2003.
Her son Michael has said he knows who took his mother, but fears reprisals from the IRA should he ever pass that information on to the police.
However, his sister, Helen McKendry who was 15 at the time of her mother's murder, said she had no fear and would be prepared to name those responsible.
She said: "What are they going to do to me? They have done so much to me in the last 42 years."
"Are they going to come and put a bullet in my head? Well they know where I live."
No one has ever been charged with the murder of the 37-year-old widow, but after years without progress in the criminal investigation there have been a series of arrests in recent weeks.
Veteran republican - 77-year-old Ivor Bell - was charged in March with aiding and abetting the murder and five others have been detained and questioned.
The recent police activity followed a decision by a US court compelling a Boston university to hand over to the PSNI recorded interviews with republicans about Mrs McConville's murder.
Mr Adams has always strenuously denied allegations levelled by former republican colleagues that he had any involvement in the murder of Mrs McConville, who was wrongly suspected of being an informer for the British Army.
In March, the 65-year-old said he would be willing to meet with police for their investigation.
His arrest on Wednesday sparked outrage from Sinn Féin who said the move was "politically motivated".
Deputy First Minister Martin McGuinness said it was an example of the "dark side" of policing trying to flex its muscles.
Prime Minister David Cameron and First Minister Peter Robinson both rejected their claims.
The prime minister was very clear that the police must be allowed to do their job and there has been no political interference in the policing process.
Secretary of State Theresa Villiers
Secretary of State Theresa Villiers revealed Prime Minister David Cameron spoke separately with both Peter Robinson and Martin McGuinness about the arrest.
She said: "We must leave the timing of arrests to police and they have to act on the evidence available to them.
"I do not think it is fair really, to ask them to take on board the political time table and indeed if they did they could be accused of exactly the type of political policing Martin McGuinness has accused them of now."
Following the arrest there has been criticism levelled at the British Government that it is more concerned with the crimes of others committed during the Troubles rather than those who perpetrated state crimes.
Ms Villiers added: "It's for the PSNI to pursue law-breakers whether they are members of the security forces or not and indeed the PSNI is investigating some members of security forces.
"This is a government that doesn't believe in amnesties and if crimes have been committed those individuals concerned should subjected to due process of law regardless if they are members of the security force or not."
She added: "I recognise the difficulties in this case and have engaged with the first ministers and would urge everyone to respond in a measured way.
"Whatever the outcome there are still problems to be fixed in Northern Ireland and the best way to do that is by the political parties working together."
On Thursday Martin McGuinness said "dark forces" were at work within the PSNI over the arrest, something Justice Minister David Ford rejected.
He said: "I see a police force with very high levels of confidence, higher than the Garda Siochana or many forces in Great Britain, and I see a police force carrying out its duties properly and appropriately, following up evidential opportunities where they present themselves and operating in conjunction with the community across a range of issues."