Sonnen was first booked to face off against Ricardo Liborio before Frank Mir agreed to step in. Now, he’ll take on Vieira during the event, which goes down September 22-24 in Finland at The Espoo Metro Arena.
Vieira has won two ADCC golds at 145 pounds, while Sonnen most recently competed at light heavyweight vs. Wanderlei Silva. He challenged twice for the UFC middleweight belt and once more for the 205-pound title.
Along with Sonnen-Vieira, Renzo Gracie takes on San Kikuta and Andre Galvao meets Claudio Calasans. Jake Shields, Gilbert Burns, Jeff Monson, Gabi Garcia and Dillon Danis are all scheduled to compete during the event.