The 12-10, party-line committee vote sends the nomination to the full Senate.
Barr previously served as attorney general from 1991 to 1993 under President George H.W. Bush and is highly respected in the conservative legal world.
Nadler said he might need the "threat" of the subpoena to get answers during the Friday session.
In part, they say Barr left open possible loopholes in his commitment to airing Mueller's findings and a broad view of presidential power that might allow Trump to interfere in Mueller and other investigations into his campaign, family or associates.More news: Acting Attorney General Matthew Whitaker Infuriates House Dems at Hearing
During the hearing, Democrats on the Committee expressed concern about a memo that Barr wrote a year ago that called the Mueller investigation into the Russian interference in the 2016 election "fatally misconceived". As the country's chief law enforcement officer, Barr would oversee the remaining work in Mueller's investigation into potential coordination between the Kremlin and the Trump campaign.
During his confirmation hearing earlier this year, Barr, 68, assured senators of his independence and said that he would not be bullied by anyone into doing something he believes is wrong if he becomes the attorney general. Democratic Senators on the Judiciary Committee grilled Barr on issues relating to the Mueller probe and executive privilege, criminal justice policy, immigration, and more.
Sen. Richard J. Durbin (D-Ill.) said he felt Barr was a "good person" and likened him to Jim Mattis - Trump's former defense secretary, who had a reputation for being independent and resigned from the administration amid disagreements with the president.
Lawmakers have raised questions about a memo Barr wrote to Justice Department leaders questioning what he saw as the "fatally misconceived" theory of Trump obstructing justice that Mueller seemed to be exploring.
But Democrats said Thursday that Barr's comments did not go far enough to reassure them.
"I don't believe Mr. Mueller would be involved in a witch hunt", Barr said.