The Galaxy announced the signing of the 24-year-old center back Wednesday. Coulibaly spent the past three years with AS Nancy in France's Ligue 2, making 45 appearances for the club.
The Galaxy announced the signing of Cabral on April 8 as a young designated player, but the 21-year-old Paris Saint-Germain youth product still hasn't joined Los Angeles while sorting out his P-1 Visa and International Transfer Certificate.
Coulibaly spent two seasons under contract with Ligue 1's Rennes before joining Nancy. He also had loan spells with US Avranches while with Rennes and Nancy.
Coulibaly is the fifth major defensive signing in the past few months by Galaxy general manager Dennis Te Kloese, who has completely rebuilt last season's leaky unit.
"Sega is a talented, versatile defender with good experience, and we believe he can continue to grow as a player with our club,'' Te Kloese said. "We are confident in his ability to contribute to our defense as we add another player who will compete along our backline."
The Galaxy are off to a strong start to the new MLS season at 2-0-0 with five goals already from star forward Javier Hernandez.