Carlo, about to enter his fourth NHL season, will earn an average of $2.85 million.
The three-year deal is worth $4.9 million annually.
"We did lot of good things last year, but didn't reach our ultimate goal."
The details of the extension have not been made public.
At Friday’s captain’s practice, he took wrist shots and one-timers and skated during drills.
"This last playoffs was big for me and my development and my growth. I feel like I'm just hitting my prime."
The Bruins goal-scorer briefly traded in his skates for soccer cleats.