The 23-year-old has made 12 appearances for the Tigers this season and done enough to impress head coach Pat Howard.
He joins his brother Louis - who has already signed a two-year contract extension - in committing to the club.
"I have done it nice and early and as a player that is always what you want - to get your future sorted out early on," Deacon told www.leicestertigers.com.
"I have got a two-year deal which I am extremely happy about. There are a lot of back-rowers here who are very good players and the club have obviously got confidence in me."