The publicists told UsMagazine.com Lively, 24, and DiCaprio, 36, "remain friends" despite the split.
No reason was given for the breakup.
The stars were first photographed together aboard director Steven Spielberg's yacht in Monte Carlo during the Cannes Film Festival last May, then were spotted in Italy, Australia, California and New York throughout the summer, UsMagazine.com noted.
Lively is a cast member of TV's "Gossip Girl." DiCaprio's film credits include "William Shakespeare's Romeo & Juliet," "Titanic," "Gangs of New York," "The Departed" and "Shutter Island."