The 19-year-old, who had an outstanding debut year in 2013 playing 18 games. agreed to terms with the club yesterday.
The club's first draft pick in the 2012 draft at No.8, Mayes is seen as one of the building blocks for the club's future under new coach Justin Leppitsch.
Mayes said he was enjoying his time in Brisbane and was satisfied the club was on the right path.
"I'm really happy to be staying with the Lions," Mayes told lions.com.au.
"The club is headed in the right direction and I'm looking forward to developing as a player with a great team."
Lions General Manager of Football Dean Warren said Mayes' signing was a positive for the club.
"Sam had a standout first year and he is the kind of player we are looking to build the club's future on," said Warren.
"We are delighted Sam has committed to another two years - it is a show of faith in the strong direction we have."
More details on Mayes' signing will be available on lions.com.au on Monday when he will speak at a media conference.
