Early career Castillo began training MMA when he joined the wrestling team at his high school in suburban Sacramento. His vice principal, who was also the wrestling coach, told Castillo that if he joined the team, he would not call his mother after seeing Castillo constantly in trouble. Castillo claims he was scared his first day at practice, "I got the [expletive] kicked out of me that day, but after that, I wasn't nervous at wrestling practice ever." After leaving private school, Castillo graduated from
Laguna Creek High School (Elk Grove, CA) and attended
Menlo College; becoming an NAIA All American in 2004. His nickname "Last Call" was given to him in college due to his ability to perform well in his team's offseason morning runs despite having been up consuming massive amounts of alcohol until
last call. Castillo made his professional debut in November 2007, fighting twice in the month, winning both fights via first round submission. After going 3-0, Castillo signed to fight on the Palace Fighting Championship's seventh card. He fought Andy Salazar winning via submission due to his tough ground and pound. He won his fifth straight fight after defeating Strikeforce veteran, Isaiah Hill. With the win, Castillo was signed with the WEC.
World Extreme Cagefighting Castillo made his debut against
Donald Cerrone at
WEC 34, replacing an injured
Rich Crunkilton. Cerrone defeated Castillo via first round armbar submission. Castillo then fought Rafael Dias at
WEC 36, winning via TKO in the second round. Four months later Castillo fought
Phil Cardella at
WEC 39. Castillo won the fight via split decision. Castillo then defeated
Ricardo Lamas, winning his third straight WEC fight. Castillo was defeated by
Shane Roller via third round submission at
WEC 44. Castillo looked to rebound from his loss to Roller when he fought
Anthony Pettis at
WEC 47, but lost via KO after getting caught flush with a head kick. Castillo defeated WEC newcomer
Dustin Poirier via unanimous decision on August 18, 2010, at
WEC 50. Castillo next faced
Will Kerr on December 16, 2010, at
WEC 53. He won the fight via KO in the first round.
Ultimate Fighting Championship In October 2010,
World Extreme Cagefighting merged with the
Ultimate Fighting Championship. As part of the merger, all WEC fighters were transferred to the UFC. On December 31, 2010, Castillo officially became a contracted UFC fighter, signing a four-fight deal with the promotion. In his UFC debut, Castillo fought
Joe Stevenson on March 3, 2011, at
UFC Live: Sanchez vs. Kampmann. Castillo controlled the entirety of the fight and won via unanimous decision. Castillo faced
Jacob Volkmann on August 14, 2011, at
UFC on Versus 5. He lost the fight via unanimous decision (29-28, 29-28, 29-28). Castillo faced
Shamar Bailey on November 19, 2011, at
UFC 139. Bailey came in 3 pounds over, which resulted being fined 20 percent of his earnings, and the bout took place at a catchweight of 158 lb. Castillo won the fight via TKO in the first round. Castillo faced
Anthony Njokuani on December 30, 2011, at
UFC 141 on five weeks notice, replacing an injured
Ramsey Nijem. Throughout the fight Castillo scored several suplex takedowns and looked to smother his opponent on the ground. He won the fight via split decision. Castillo faced
John Cholish on May 5, 2012, at
UFC on Fox 3. He defeated Cholish via unanimous decision (30-27, 30-27, 30-27). Castillo was expected to face
Michael Johnson on September 1, 2012, at
UFC 151. However, after
UFC 151 was cancelled, Castillo/Johnson was rescheduled and took place on October 5, 2012, at
UFC on FX 5. After a dominant first round put in by Castillo, where he nearly finished Johnson via strikes and then with a submission attempt, he was knocked out cold with a counter left at 1:06 of the second round. Castillo faced
Paul Sass on February 16, 2013, at
UFC on Fuel TV: Barão vs. McDonald. Castillo used a superior top game and ground and pound en route to a unanimous decision victory. Castillo was expected to face
Bobby Green on July 27, 2013, at
UFC on Fox 8. However, in mid-July, Green pulled out of the bout citing an injury and was replaced by
Tim Means. He won the fight via unanimous decision. Castillo faced
Edson Barboza on December 14, 2013, at
UFC on Fox 9. After a dominant first round by Castillo, Barboza was able to rally over rounds two and three, and defeated Castillo via majority decision in a bout that earned both participants
Fight of the Night honors. Castillo was briefly linked to a bout with
Isaac Vallie-Flagg on April 26, 2014, at
UFC 172. However, the UFC removed Vallie-Flagg from the bout in favor of a match up with
Takanori Gomi, while Castillo instead fought against
Charlie Brenneman. Castillo won the fight via knockout in the second round. However, after
UFC 176 was cancelled, Castillo/Ferguson was rescheduled and took place on August 30, 2014, at
UFC 177. Castillo lost the back and forth fight via split decision. Castillo was expected to face
Rustam Khabilov on January 3, 2015, at
UFC 182. However, Khabilov pulled out of the bout due to alleged
visa issues and was replaced by
Paul Felder. Castillo lost the bout via knockout due to a spinning backfist in the second round. A rescheduled bout with
Rustam Khabilov was expected to take place on July 25, 2015, at
UFC on Fox 16. However, for a second time, Khabilov was removed from the pairing due to alleged
visa issues. Castillo faced
Jim Miller at the event. He lost the fight by split decision. Castillo faced
Nik Lentz on December 19, 2015, at
UFC on Fox 17. He lost the fight by split decision. On January 29, 2016, Castillo was released from the UFC. He has since retired from mixed martial arts. ==Championships and accomplishments==