The former couple reunited at the Dior Homme Cocktail Reception, and posed for photos while laughing and palling around together at the event, reported People magazine.
Bosworth, donning a black dress and red lipstick, was joined at the party by her husband, director Michael Polish.
The "Pirates of the Caribbean" star and Bosworth called off their two year relationship in January 2005, in what their publicist said was a mutual decision based on their conflicting work schedules.
Bosworth married Polish in 2013, after they met and fell in love on the set of Big Sur in 2011. The sparks flew and it was love at first sight between the director and his leading actress on the film.
Both actors have recently completed new movies: Bloom is reprising his role as Will Turner in Pirates of the Caribbean: Dead Men Tell No Tales, and Bosworth recently finished Life on the Line costarring John Travolta.
