In September 2010 Warren won the Bellator Featherweight Championship defeating Joe Soto. In March 2012 he lost the Bellator Featherweight Championship to Pat Curran. Warren defeated Rafael Silva in May 2014 to win the Interim Bellator Bantamweight Championship. In October 2014 he defeated Eduardo Dantas to win the Undisputed Bellator Bantamweight Championship before losing it to Marcos Galvao in March 2015. As of that fight he has a professional MMA record of 12-4 and is ranked the #7 Bantamweight in the world.