Firrito played his 150th game in round one this season and has become one of the Kangaroos' most consistent performers since being elevated from the rookie list in 2003.
“Mick has a terrific opportunity to assume more leadership responsibility with the retirement of Brady Rawlings,” Chief of Football Donald McDonald said.
“He's one of our more experienced players and he along with Scott Thompson, Nathan Grima and Scott McMahon are the nucleus of a back-line which we think will be a real strength for us next year."
The 27 year-old has signed with the club until the end of 2012.
Campbell, 24, played the final eight matches this year to take his career tally to 67.
The exciting small-forward will remain at Aegis Park until the end of 2013 after signing a new deal.
“We’re extremely pleased to have Matty re-sign with the club for another two seasons," McDonald added.
“For him personally it’s a great opportunity to build on his strong finish to the year following some bad luck with injuries."
In round 20, Campbell kicked four last quarter goals and five for the match against Hawthorn.
Campbell was also promoted from the club's rookie list, in 2007.
