Strikeforce

Melendez held the Strikeforce Lightweight Championship belt for two years before losing it on June 27, 2008, to Josh Thomson by unanimous decision (50–45, 50–45, 50–45) at Strikeforce: Melendez vs. Thomson.

On August 15, 2009, Melendez was again set to rematch Josh Thomson at Strikeforce: Carano vs. Cyborg but Thomson was not cleared to fight, due to lingering problems with his leg. Mitsuhiro Ishida was selected to replace Thomson in what became Melendez' first Interim title defense.

On December 19, 2009, Melendez fought Josh Thomson to unify the Strikeforce Lightweight Championship belts.^[6] Melendez won the fight via unanimous decision to become the Strikeforce Lightweight Champion. With the win he also avenged the second of his only two losses to date.

Melendez successfully defended the Strikeforce Lightweight Championship against current DREAM Lightweight Champion and former Shooto Middleweight Champion Shinya Aoki on April 17, 2010.^[7]

A rematch between Melendez and Tatsuya Kawajiri took take place on April 9, 2011, at Strikeforce 33 in April.^[8] Melendez dominated his opponent showing excellent striking, knocking down Kawajiri with a right hand near the beginning of the fight. Melendez then again knocked down Kawajiri with a combination of knees to the body and a right hook followed by a right uppercut. The beginning of the end came when Melendez sprawled one of Kawajiri's takedowns and then began landing short left hands which knocked Kawajiri down into half-guard where Melendez began landing vicious right elbows before the referee stopped the fight declaring Melendez the winner by TKO 3:14 into the first round.

Melendez faced Jorge Masvidal next. UFC president Dana White briefly put the bout in question when he revealed to reporters that he was working to bring Melendez into the UFC fold "ASAP" with the possibility of Melendez entering with an immediate shot at the belt.^[9] Melendez eventually defended his title against challenger Jorge Masvidal at Strikeforce: Melendez vs. Masvidal. He won the fight via unanimous decision.

Melendez took on Josh Thomson in a rubber match for the Strikeforce Lightweight Championship at Strikeforce: Barnett vs. Cormier in San Jose, California on May 19, 2012. He won the fight via split decision. Fans did not agree with the decision and Josh Thomson was visibly disappointed by the decision. Booing immediately followed the decision and continuously throughout Melendez's post fight interview. Thomson, although not pleased with the decision, showed class in defeat by asking the crowd to stop booing and support the local fighter.

Melendez was expected to face Pat Healy for the Strikeforce Lightweight Championship on September 29, 2012, in Sacramento, California. It was announced on September 22, 2012, that Melendez suffered an injury and had to withdraw from the fight. Due to Melendez' injury, Showtime opted not to air the card without the main event, thus causing Strikeforce to cancel the card becoming the second MMA card cancelled within a month under the Zuffa organization.^[10]

The bout with Healy was rescheduled for January 12, 2013 at Strikeforce: Marquardt vs. Saffiedine, but again, Melendez pulled out of the bout citing a shoulder injury.^[11]

Ultimate Fighting Championship

The Strikeforce promotion was dissolved into the UFC by parent company Zuffa on January 12, 2013. Melendez received an immediate UFC title shot and made his promotional debut against Benson Henderson on April 20, 2013, at UFC on Fox 7.^[12] Melendez lost a split decision in a closely contested bout.^[13]

In his second UFC fight, Melendez faced Diego Sanchez on October 19, 2013, at UFC 166.^[14] He won the fight via unanimous decision. The win also earned him his first Fight of the Night award.^[15] On UFC.com Joe Rogan called the brawl between Melendez and Sanchez the best he's ever seen.

Melendez was scheduled to face Khabib Nurmagomedov at UFC 170.^[16] However, the fight was later cancelled due to undisclosed reasons.^[17]

After negotiating with the UFC for his new contract, there was speculation that Melendez may sign with Bellator.^[18][19] In the process, Melendez also got an offer from World Series of Fighting.^[20] He then agreed to sign with Bellator, but the UFC had the right to match their offer.^[21] Melendez ultimately re-signed with the UFC after he was given the opportunity to serve as a coach on The Ultimate Fighter 20, opposite UFC Lightweight Champion Anthony Pettis, the two would face each other at UFC 181 on December 6, 2014.^[22][23] He lost the fight via guillotine choke in the second round.

Melendez then faced Eddie Alvarez on June 13, 2015, at UFC 188.^[24] He lost the fight by a close split decision.^[25]

Melendez was tabbed as a short notice replacement to face Al Iaquinta on July 15, 2015, at UFC Fight Night 71, taking the place of Bobby Green.^[26] However, Melendez was removed from the card on July 6 after it was revealed that he tested positive for performance-enhancing drugs after his previous fight at UFC 188. In addition, Melendez was suspended for one year from the date of the bout for violation of the UFC Fighter Conduct Policy.^[27]

Melendez next faced Edson Barboza on July 23, 2016, at UFC on Fox 20.^[28] Melendez lost the fight by unanimous decision.^[29]

Melendez faced Jeremy Stephens in a featherweight bout on September 9, 2017, at UFC 215.^[30] He lost the fight via unanimous decision.^[31] Both participants were awarded Fight of the Night honors for their performance.^[32]

Melendez was scheduled to face Arnold Allen on November 30, 2018, at The Ultimate Fighter 28 Finale.^[33] However, Melendez pulled out of the fight on November 5 and was replaced by Rick Glenn.^[34]

Melendez faced Arnold Allen on July 6, 2019, at UFC 239.^[35] He lost the fight via unanimous decision.^[36]

On November 11, 2019, it was reported that Melendez was released by UFC.^[37]