Obama praised Booker's efforts as Newark mayor and said that he "has dedicated his life to the work of building hope and opportunity in communities where too little of either existed." In a statement released by Booker's campaign, the president said that Booker has been building coalitions and helping the middle class since his college days at Stanford University.
Booker is leading the Republican nominee, Steve Lonegan, by 16 percentage points in a recent poll.
Obama specifically praised the Democratic nominee as someone who will work with him on gun control issues.
"His passion for his city has helped create new jobs and attract some of America's top businesses to Newark," Obama said. "Cory will be an important partner in our efforts to reduce gun violence, give every American a fair shot in a global economy, and make our country stronger."
The endorsement comes a week after Booker and Lonegan easily captured their respective party nominations for the Oct. 16 special election, which has been called to fill the seat left open by the June death of Sen. Frank Lautenberg (D).
Lonegan, a tea party favorite, has picked up his own string of endorsements this week, with New Jersey Gov. Chris Christie (R) and Lt. Gov. Kim Guadagno (R) backing him on Tuesday. He is scheduled to be endorsed by short-term U.S. Sen. Jeff Chiesa (R), Christie's appointee to fill the seat until October, on Wednesday. Lonegan, the former mayor of Bogota, N.J., spent the last seven years heading the New Jersey chapter of Americans for Prosperity, the Koch brothers-affiliated group. He has made opposition to Obamacare a core part of his platform.
In Wednesday's statement, Booker said that he was "humbled" by Obama's endorsement.
"The president has taken on the difficult fights. He worked to turn around our economy, to make high-quality, affordable health care available to every American and to keep our country safe," Booker said. "I look forward to continuing to work with him to advance an agenda that spreads prosperity and ensures that our nation realizes the promise of its founding."
This is the second time Obama has backed a Democrat in a special U.S. Senate race this year. The president endorsed then-Rep. Ed Markey in his successful bid to win Massachusetts' June special election.
UPDATE: Lonegan told The Huffington Post Wednesday that he is not surprised by Obama's endorsement of Booker, saying that he believes the election will turn into a referendum on the president. He specifically contended that Obama has failed to lead the U.S. in the areas of the economy, health care and the National Security Agency.
"Cory Booker will be a rubber stamp for Obama," Lonegan said. "New Jersey and the country are sick and tired of Obama's lies."
Lonegan challenged Booker to bring Obama to New Jersey for campaign events. He said that seeing Obama and Booker campaign together would make voters realize that Obama hasn't helped the Garden State. The Republican believes the Obama endorsement will help him and said that Booker is more liberal than the president.
"Cory Booker has proposed policies that are far to the left of Obama. He wants to go more extreme," Lonegan said.