Dawson, who played 18 games last season and was at his best in the club's two finals, has signed a two-year extension that will keep him at his third club until the end of the 2015 season.
Mayne has signed a three-year extension that will see him remain at the club until the end of the 2016 season.
General manager of player management Brad Lloyd said the club was pleased to secure two valued members of the squad.
"Both players are very important components of our structure," Lloyd said.
"Chris had an excellent 2012 playing as a forward, and Zac was part of a solid defensive group that really grew as a unit last year."
Mayne took his game to a new level in 2012, playing all but one match and kicking 39 goals to finish runner-up in the Doig Medal behind run-with specialist Ryan Crowley.
He was selected with pick 40 in the 2007 NAB AFL Draft, and has played 81 games since making his debut in round two of the following year.
Dawson reunited with coach Ross Lyon last season and was a key member of Fremantle's back six, with the team conceding an average of just 77 points per game (ranked No.2 in the AFL).
He is valued for his finals experience and held Geelong forward Tom Hawkins goalless in Fremantle's elimination final win at the MCG.
Chris Mayne is a forward in NAB AFL Fantasy. He averaged 73.86 points in 2012. Register your team at our AFL Fantasy Hub.
Nathan Schmook is a reporter for AFL Media. Follow him on Twitter: @AFL_Nathan
