Medeiros grew up in Wai'anae Hawaii and at a young age began training in Karate. He is of Filipino and Native Hawaiian descent, known as Hapa Pukiki and Hapa Pilipino. Medeiros wrestled for his Waianae High School wrestling team, placing third in the state wrestling tournament his senior season. Yancy credits Kawika Pa'aluhi, an early pioneer of MMA in Hawaii, with motivating him to train and pursue a career in MMA.
Medeiros began his career 4-0 before defeating EliteXC veteran Po'ai Suganuma at Destiny MMA: Pier Fighter 1. After winning two more fights to bring his record to 7-0, fighting as a Light Heavyweight, he then signed with Strikeforce.
Strikeforce
In his Strikeforce debut, moving down to Middleweight, Medeiros defeated Raul Castillo by unanimous decision at. No. His next fight came against Gareth Joseph which Medeiros won via first-round KO due to punches at. Medeiros was expected to face John Salter at Strikeforce Challengers: Woodley vs. Saffiedine. However, Medeiros was forced from the bout with an injury.
On January 31, 2013, it was announced that Medeiros would be brought over to the Ultimate Fighting Championship as part of the Strikeforce transition. He dropped two weight classes to Lightweight and made his UFC debut against Rustam Khabilov on April 27, 2013 at UFC 159. The fight ended in unusual fashion as Medeiros dislocated his thumb during a takedown by Khabilov early in the first round, resulting in a TKO victory for Khabilov as Medeiros was unable to continue. Medeiros took on Yves Edwards at UFC Fight For The Troops 3 on November 6, 2013. He won by KO in the first round. The win, however, was subsequently overturned when Medeiros tested positive for marijuana in his post-fight drug test. Medeiros was expected to face promotional newcomer Joe Ellenberger on April 26, 2014 at UFC 172. However, in the week leading up to the event, Medeiros was pulled from the Ellenberger bout in favor of a match up on the main card with Jim Miller after his scheduled opponent Bobby Green pulled out of the bout. Medeiros lost the fight via submission in the first round. Medeiros was expected to face Justin Edwards on August 30, 2014 at UFC 177. However, Edwards pulled out of the event in the days leading up to the event citing an injury. Medeiros instead faced promotional newcomer Damon Jackson. Medeiros won the fight by submission in the second round. The win also earned Medeiros his first Performance of the Night bonus award. Medeiros faced Joe Proctor on December 12, 2014 at. Medeiros won the fight in the first round after dropping Proctor with a spinning back kick to the body and securing a guillotine choke to earn the submission. The result also earned Medeiros a Performance of the Night bonus. Medeiros was expected to face Tony Ferguson on February 28, 2015 at UFC 184. However, Medeiros pulled out of the bout citing injury and was replaced by Gleison Tibau. Medeiros faced Dustin Poirier on June 6, 2015 at UFC Fight Night 68. He lost the fight via TKO in the first round. Medeiros faced John Makdessi on December 12, 2015 at UFC 194. He won the fight by split decision. Medeiros next faced Francisco Trinaldo on May 14, 2016 at UFC 198. He lost the fight via unanimous decision. Both participants were awarded Fight of the Night honors. Medeiros faced Sean Spencer in a welterweight bout on September 10, 2016 at UFC 203. He won the fight via submission in the second round and was awarded a Performance of the Night bonus. Medeiros was expected to face Li Jingliang on January 28, 2017 at UFC on Fox 23. However, in early January, Medeiros pulled out for undisclosed reasons and was replaced by promotional newcomer Bobby Nash. Medeiros faced Erick Silva on June 3, 2017 at UFC 212. He won the fight via TKO in the second round. Medeiros faced Alex Oliveira on December 2, 2017 at UFC 218. He won the back-and-forth fight via TKO in the third round. The win also earned him his second Fight of the Night bonus award. Medeiros faced Donald Cerrone on February 18, 2018 at. He lost the fight via technical knockout out in round one. Medeiros was expected to face Mike Perry on July 7, 2018 at UFC 226. However, Medeiros pulled out of the fight on June 27 citing a rib injury and was replaced by Paul Felder. Medeiros faced Gregor Gillespie in a lightweight bout on January 19, 2019 at UFC Fight Night 143. He lost the fight via TKO in the second round. Medeiros faced Lando Vannata on February 15, 2020 at. He lost the fight via unanimous decision.
Personal life
Medeiros started off his career fighting at light heavyweight. He then moved down to middleweight and eventually made his lightweight debut at UFC 159. Medeiros credits Nick Diaz and Nate Diaz for changing his diet and work ethic which allowed him to lose weight and move down in weight classes.
Championships and achievements
Ultimate Fighting Championship
*Fight of the Night vs. Francisco Trinaldo and Alex Oliveira
