The star has joined another original Pie favourite, Seann William Scott, who also sought treatment in rehab recently (Mar11) for "health and personal issues".
Klein will return as Chris 'Oz' Ostreicher in the fourth installment of the teen comedy, titled American Reunion.
Following his success in the films, Klein fell from grace after twice being arrested for drink driving - once in 2005 and again in 2010
After he was caught for the second time last year (10), Klein checked himself into a rehabilitation centre in a bid to kick his alcohol issues.
And he's now putting his troubles behind him - earlier this year (11) he signed up to star opposite Elijah Wood in new TV show Wilfred and he's now set to resurrect his American Pie character.
Klein's representative, Jaime Primak, tells People.com the star is "very excited to reunite with the original cast."
Other original castmembers Jason Biggs, Alyson Hannigan, Tara Reid and Eugene Levy will also be a part of the sequel.