Lautenberg, already the third oldest member of Congress at age 84, cruised past Republican Dick Zimmer in an easy victory.
The Associated Press declared him the winner based on an analysis of voter interviews conducted for the AP by Edison Media Research and Mitofsky International.
Lautenberg will be 90 when his next six-year term expires.
New Jersey's U.S. Senate race was largely overshadowed by the presidential contest. Both candidates ran a low-key campaign, appearing together to debate only in the final week of the contest.
Zimmer, who was outfinanced and outspent by Lautenberg, failed to get his name or message out to most voters. Though he is a former congressman, most voters in independent polls said they hadn't heard of him.