Warren originally came to Washington as head of the government's official bailout watchdog, and later served as President Obama's architect of the Consumer Financial Protection Bureau (CFPB), which was created by the Dodd-Frank financial reform law.
Heitkamp also will join both the Agriculture and Small Business panels.
“I am excited to work with the members of our expanded majority. Our caucus is more diverse than ever, with a record 16 female Democratic senators serving in the next Congress,” said Senate Majority Leader Harry Reid (Nev.).
"These committee assignments will allow all members of our caucus to bring their unique talents and expertise to bear as we work together to advance the interests of the middle class."
The powerful Senate Finance Committee added Sens. Sherrod Brown (D-Ohio) and Michael Bennet (D-Colo.), replacing the retiring Sens. Kent Conrad (D-N.D.) and Jeff Bingaman (D-N.M.).
Bennet, who was appointed to the seat in 2009 and elected in 2010, will shift from banking to finance. He picked up the plum seat after agreeing to take the reins of the Democratic Senatorial Campaign Committee.
“He has proven himself to be an up-and-coming leader who is always willing to reach across party lines,” Baucus said.
Baucus also praised Brown, who won a second six-year term in November, as "a fierce advocate for of the middle class."
Brown, who has opposed trade deals over concerns that they would force companies to ship jobs overseas, backed a bill last week to grant permanent normal trade relations (PNTR) with Russia. He argued that the bill included improvements over other PNTR deals and that it will help U.S. exporters.
“My biggest priority is to help build the middle class, and this committee provides a great opportunity to do so: from ensuring a fair tax code, to standing up for Ohio's manufacturers and workers when it comes to foreign trade, to protecting Social Security and Medicare,” Brown said.
Senate Agriculture added Indiana's Joe Donnelly, while Appropriations added three to its rolls, all returning lawmakers: Sens. Tom Udall (N.M.), Jeanne Shaheen (N.H.) and Jeff Merkley (Ore.).
Sen. Patty Murray (Wash.), the new chairman of the Budget Committee, will add newly elected Sens. Tammy Baldwin (Wis.), Tim Kaine, the former governor of Virginia who won a tight race against former Sen. George Allen, and Angus King, an independent who opted to caucus with Democrats.
All survived close races to earn their first term in the upper chamber.
The Joint Economic Committee will add freshman Sen. Chris Murphy (Conn.) and Sen. Martin Heinrich, a House member since 2009, who takes Bingaman's spot.
The Democratic Steering Committee approved the assignments on Wednesday.
The assignments are subject to approval by the full Democratic Caucus and approval of an organizing resolution by the full Senate when the 113th Congress convenes in January.