Stephen Amell joins Megan Fox as April O'Neil and Will Arnett as Vern Fenwick.
David Green is directing the sequel, which has a June 3, 2016 release.
No specific plot details are known, but both Bebop and Rocksteady have also been confirmed.
It's reported Stephen Amell beat out a half-dozen actors for the role, with it said Amell nabbed the role do to his good chemistry with Megan Fox.
Update: Amell confirmed the news on Facebook as well:
"What a fantastic day. Honored to play Casey Jones in #TMNT2."