The Italy international tighthead prop is approaching 100 appearances for the club and has been a big hit with team-mates and supporters since his arrival at Welford Road in 2006.
Named Premiership Player of the Year in his debut season in 2006/07, Castrogiovanni has won three league titles with Tigers in his first four years with the club as well as playing in the 2009 Heineken Cup Final and 2007 EDF Energy Cup Final.
Tigers director of rugby Richard Cockerill said: “Castro is a world-class player and we are delighted that he has decided to stay here.
“He has moved to the top levels of the game during his time with us and our environment certainly suits him. He is happy in Leicester, he is very popular with the supporters and with his team-mates.
“Everyone knows that Castro has had opportunities to go elsewhere, but he has shown his commitment to the Tigers and we’re looking forward to his continued contribution in the future.
“Together with Dan Cole and Julian White, we have a group of top-class tighthead props and we want to keep them together to work as a group. With the increasing intensity of the professional game it is certainly an advantage to have top-class options available and to be able to keep players fresh in order to perform consistently at their best.”
Tigers chairman Peter Tom CBE said: “It is great news for the club that Castro has agreed to stay.
“He attracted offers from elsewhere, but in considering all of his options, including his relationship with this club and its supporters, and his lifestyle and business interests here, he has decided that this is where his future lies.
“A large number of our supporters and season ticket holders own shares in the club and thousands of them contribute in terms of ticket sales so they all have a part to play.
“We have tremendously loyal supporters and one of the reasons behind our success is that the revenue we receive from season ticket sales allows us to maximise expenditure on the squad within the salary cap where some other clubs may be unable to do so.
“We also invest significantly in support of the playing side, in preparation, conditioning and training facilities, and in the quality of our back-room staff, all with the aim of maintaining our success in the long term.
“All of these factors are important when players are considering a future with us.
“There is a unique culture at this club which has been established over many years and players know they can develop with us inside a winning, successful environment.”