With about 50 percent of precincts reporting, Booker had 60 percent of the vote, trailed by Rep. Frank Pallone at 22 percent, Rep. Rush Holt at 13 percent and state Assembly Speaker Sheila Oliver at less than 5 percent, The Washington Post reported.
Booker will face Steven M. Lonegan, a former mayor of Bogota, N.J., in an Oct. 16 special election to fill the 15 months remaining in Lautenberg's term. Lonegan defeated physician Alieta Eck in the Republican primary.
"Mayor Cory Booker is going to be the kind of senator New Jersey can be proud of, and I congratulate him on his victory tonight," Sen. Michael Bennet, chairman of the Democratic Senatorial Campaign Committee, said in a statement. "I look forward to working side by side with Cory, and supporting his re-election next November."
Lautenberg, a Democrat, served in the U.S. Senate from 1982-2001 and returned to the Senate in 2003, serving until his death at age 89 June 3.
New Jersey Gov. Chris Christie in June appointed state Attorney General Jeff Chiesa to serve as interim senator until after the special election.
The Democratic primary victor is heavily favored to win Lautenberg's seat, largely because Democrats outnumber Republicans in New Jersey by some 700,000 registered voters.