The 21-year-old has put pen-to-paper on a two-year deal at Ewood Park, subject to international clearance.
A powerful presence at the back and a goal threat from set-plays, Songo'o has been training with Rovers since early July and impressed in the pre-season friendlies against Wrexham and Portimonense.
The French-born centre back hails from a famous footballing family. His dad, Jacques, is a former Cameroon international goalkeeper and his older brother, Franck, came through the ranks at Barcelona.
The Rovers new boy also spent the majority of his youth career in Spain, playing for the likes of Deportivo La Coruna and Real Zaragoza, before having spells with Sabadell and Pobla de Mafumet.
He recently enjoyed a six-month spell in America, signing for MLS side Sporting Kansas City in December, before going out on loan to Orlando City.
At international level, Songo'o represented Cameroon at the 2011 African Youth Championship in South Africa, helping his country reach the final and qualify for the 2011 FIFA Under-20 World Cup. He was subsequently selected for the tournament and played in a 1-0 victory over Uruguay in the final group game, which secured Cameroon's place in the knockout stage.