MMAJunkie.com first reported that the bout was in the works and ProMMAnow.com has since confirmed the news.
Stevenson started his UFC career 5-1 and earned a shot at then-lightweight champion B.J. Penn at UFC 80. However, Stevenson suffered a second round submission loss and has since gone 3-4. In his last fight at UFC 124, Stevenson got knocked out by Mac Danzig after only 94 seconds courtesy of a well-timed left hook.
While Stevenson is in need of a win, Castillo will hope to make an impression in his first UFC appearance after going 5-3 in the WEC prior to the merger of the two organizations. Following back-to-back losses to Shane Roller and Anthony Pettis, Castillo won his last two fights against Dustin Poirier and Will Kerr.