People.com said the couple exchanged vows in the penthouse of the Hard Rock Hotel Saturday night -- a day after the couple got engaged and picked up a marriage license.
Federline, 35, and Prince, 30, have been together since 2008. They have a daughter whose second birthday is next week, the celebrity news website said.
Federline and Spears were married in 2004 and divorced in 2006 and have two sons.
The former backup dancer was previously engaged to actress Shar Jackson from 2001-04. They have a son and daughter together.