The woman is being held on suspicion of the preparation of terrorist acts, the BBC reports.
According to the AP news agency, the woman is Mona Thwany, Abdulwahab's widow.
She was arrested on Tuesday in Luton, north of London, the same town where she and Abdulwahab had been living with their three children prior to the attack.
Thwany was questioned at a police station in central London before being released on bond, the BBC reported
“I can confirm that the Metropolitan Police arrested a person yesterday for the preparation of terrorist crimes and that the investigation so far shows that there may be a connection to the terror attack in Stockholm in 2010,” Sara Qvarnström, a spokesperson for Swedish security service Säpo, told the TT news agency.
Abdulwahab, a 29-year-old whose family fled from Iraq to Sweden in 1991, blew up himself and his car in a deserted side-street near Drottninggatan, one of Stockholm's busiest pedestrian thoroughfares, on December 11th, 2010, injuring two people.
Before the attack, he had lived in Luton, and had graduated with a degree in sports therapy from the city's university seven years earlier.
In March, a 30-year-old man was arrested in Glasgow, Scotland in connection to the investigation to Abdulwahab and was later charged with with crimes related to using money or property for terrorist purposes and fundraising.
Abdulwahab was carrying a cocktail of explosives and is believed to have mistakenly set off a small explosion that killed him before he could carry out what appears to have been a mission to kill "as many people as possible," a Swedish prosecutor said days after the attack.
An Islamist website, Shumukh al-Islam, posted a purported will by Abdulwahab which said he was fulfilling a threat by Al-Qaeda in Iraq to attack Sweden.
Shortly before the explosions, Säpo and the TT news agency received an email with audio files in which Abdulwahab is heard telling "all hidden mujahedeen in Europe, and especially in Sweden, it is now the time to fight back."
Thwany was previous said she was unaware of her husband's plans.
"He never gave off any clues that he was going to blow himself up," she said in an interview with the News of the World in early January, adding that she "totally condemns terrorism".
"I had no knowledge that he could do anything like that. If I had known, I would have stopped him."