Tigers cub captain Flood told the Toulouse club website: "The club symbolises French rugby. There has such a history in this club which is respected in the rugby world. I have found many similarities between the history in Toulouse and Leicester, which is one of the reasons that made me want to join this club.
“I hope to live the same great adventure in Toulouse that I've lived in England. I have the opportunity to see the differences there may be between what I'm used to and how everything is done in France, particularly in terms of training and preparation.”
Flood, 28, joined Tigers in 2008 and has made more than 100 appearances for the club, scoring 1,300 points. He also has 60 England caps.
Tigers director of rugby Richard Cockerill said: "Toby told us some time ago that he would be moving on in the summer. He has been a very important player for us and he will continue to be an important player for us for the rest of this season before he moves to France. We will wish him well."