The team announced the signings on its Twitter account Wednesday, a day after the NHL's free agency period opened.
Bernier, a nine-year NHL veteran, returns for a fourth season in New Jersey, where he's established a role as a checking-line forward. He had three goals and nine assists in 78 games last season. Overall, he has 88 goals and 104 assists for 192 points in 542 career games.
Gionta has spent four seasons in New Jersey, during which he has nine goals and 17 assists for 26 points in 127 career games.
The signings came a day after New Jersey signed free agent forwards Mike Cammalleri and Martin Havlat.