Garland, 68, had been nominated to the Supreme Court by President Barack Obama.

President-elect Joe Biden is expected to name Judge Merrick Garland to serve as his attorney general, multiple sources familiar with the transition told ABC News Wednesday, marking one of Biden’s final and most significant Cabinet appointments prior to his inauguration on Jan. 20.

Garland, 68, serves as the chief judge of the U.S. Court of Appeals for the D.C. Circuit and had been nominated to the Supreme Court by former President Barack Obama to fill the vacancy left by Justice Antonin Scalia. But he was never given a confirmation hearing by the Republicans in the Senate, who held the vacancy open for President Donald Trump to fill.

In addition to Garland, Biden is also expected to name former Homeland Security adviser Lisa Monaco as his deputy attorney general and Vanita Gupta, the former head of the Civil Rights Division at the U.S. Department of Justice as his assistant attorney general, two sources told ABC News.

Garland’s anticipated nomination comes as Democrats expect to take the Senate majority following the Georgia Senate runoff races, which would likely pave the way to a smoother confirmation process for Biden’s nominees. A simple majority in the Senate is needed for confirmation.

It would also give Biden and Senate Democrats the opportunity to replace Garland on what is considered the nation’s second-highest court.

If confirmed, Garland will assume leadership over a department with more than 100,000 federal employees that repeatedly found itself at the epicenter of politically charged controversies during the Trump administration, in addition to being the target of a barrage of attacks from Trump himself.

In the role, Garland would be confronted with pressing challenges, including the task of overseeing the ongoing criminal tax investigation of Hunter Biden, Biden’s son.

Following the controversial tenure of former Attorney General William Barr, who was assailed by current and former officials in the department for his interventions in matters of direct interest to Trump, Biden has said he hopes to restore a wall of independence between the White House and DOJ headquarters.

“I promise you, my Justice Department will be totally on its own, making its judgments about how they should proceed,” Biden told reporters in December.

Jamie Gorelick, a former deputy attorney general and longtime friend and mentor to Garland, commended Biden on the expected nomination.

“Merrick Garland is the perfect person to lead the Justice Department at this moment. He fulfills Joe Biden’s promise to return independence to the Department of Justice. He is an esteemed judge and has been for 23 years. But before that, he sat at every seat around the table at the Justice Department,” Gorelick said.

Garland previously served in the Department of Justice as deputy assistant attorney general for the Criminal Division and then as principal associate deputy attorney general, overseeing high-profile federal cases in the roles, including the Oklahoma City Bombing in 1995.

It remains to be seen how progressives and those calling on Biden to choose a person of color to lead the department that will spearhead criminal justice reform will view Garland’s expected nomination.

Before the news of Garland’s expected nomination, Sen. Bernie Sanders (I-Vt.) expressed skepticism about Garland filling the role.

“I don’t know Mr. Garland very well. But I think we could probably have a stronger progressive than him,” Sanders said on “This Week with George Stephanopoulos.”

ABC’s Katherine Faulders, Benjamin Siegel, Mike Levin and Desiree Adib contributed to this report