Early career Miller had his first professional fight on November 19, 2005, against Eddie Fyvie at Reality Fighting 10. Miller controlled the fight and earned a unanimous decision. Miller earned two more victories in the promotion over
Kevin Roddy and Joe Andujar, both via the first-round submission. The quick victories earned Miller a title shot and he fought Muhsin Corbbrey for the Reality Fighting Lightweight Championship. Miller mounted Corrbrey in the second round and battered his opponent before securing an armbar for the victory. In his first title defense, Miller took on future UFC Lightweight Champion
Frankie Edgar at Reality Fighting 14. Edgar controlled the fight, but Miller secured a tight guillotine late in the final round. Edgar fought through the choke to earn the unanimous decision. In the weeks prior to Reality Fighting 14, Planet Jiu-Jitsu closed down. Miller began training at AMA Fight Club in
Whippany, New Jersey with his brother Dan in January 2007.
Ultimate Fighting Championship 2008 Jim and his brother Dan signed with the UFC in July 2008. Miller made his debut at
UFC 89 where he defeated
David Baron in the third round. This win earned Miller his first
Submission of the Night bonus award. Miller next acted as a late replacement for
Frankie Edgar against
Matt Wiman at
UFC: Fight for the Troops. Miller dominated Wiman for three rounds, winning via unanimous decision (30-27, 30–27, 30–26). The fight also earned both fighters the
Fight of the Night bonus award.
2009 Miller next faced
Gray Maynard on March 7, 2009, at
UFC 96. He lost the fight via unanimous decision. Miller next faced
The Ultimate Fighter winner
Mac Danzig on July 11, 2009, at
UFC 100, and won in a one-sided unanimous decision. Miller was scheduled to face
Thiago Tavares on September 19, 2009, at
UFC 103, but Tavares was forced to drop out due to a knee injury suffered while training. UFC newcomer Steve Lopez stepped in to replace Tavares. Both fighters exchanged competitively on the feet, but Miller won after Lopez injured his shoulder in round two.
2010 Miller was expected to face
Tyson Griffin on January 2, 2010, at
UFC 108, but an injury forced Griffin off the card.
Sean Sherk agreed to step up from the undercard and fight Miller, rather than his original opponent in
Rafaello Oliveira. However, Sherk pulled out of the fight because of a cut that required many stitches; returning veteran
Duane Ludwig was named as Sherk's replacement. Miller looked comfortable and sharp on his feet exchanging with the seasoned striker in Ludwig and scored a knockdown halfway through the round with a fast combination. Miller swarmed to secure an armbar, winning by submission at 2:31 of the first round. Miller faced
Mark Bocek on March 27, 2010, at
UFC 111. After three closely contested rounds, Miller was awarded the unanimous decision win. Miller fought
Gleison Tibau at
UFC Fight Night 22 winning via unanimous decision. Miller was able to use his improved footwork to outstrike Tibau and stuff most of his takedowns. Miller faced touted prospect
Charles Oliveira on December 11, 2010, at
UFC 124. Miller defeated Oliveira via a first round kneebar to extend his winning streak to six and earning the
Submission of the Night bonus.
2011 Miller defeated
WEC import,
Kamal Shalorus on March 19, 2011, at
UFC 128. Miller won the fight via TKO in the third round, after landing an uppercut and knee to Shalorus's face. Miller faced
Benson Henderson on August 14, 2011, at
UFC on Versus 5. He lost the fight via unanimous decision (30-27, 29–28, 30–26). He later revealed that he was battling
kidney infection and
mononucleosis when cutting weight for the fight.
2012 On January 20, 2012, he faced
Melvin Guillard at
UFC on FX 1. After being rocked early by a knee and punches from Guillard in the first round, Miller was able to get the fight to the ground and submit Guillard with a rear naked choke. This win earned Miller his third
Submission of the Night bonus award. Miller next faced
Nate Diaz on May 5, 2012, in the main event on
UFC on Fox: Diaz vs. Miller. He lost the fight via submission, for the first time in his professional career, in the second round due to a guillotine choke. Miller faced
Joe Lauzon on December 29, 2012, at
UFC 155, replacing an injured
Gray Maynard. He won the fight via unanimous decision, with the performance earning both participants
Fight of the Night honors. The win also gave Miller the most all-time wins in UFC lightweight history.
2013 Miller faced
Pat Healy on April 27, 2013, at
UFC 159. He lost the back-and-forth fight by submission in the third round. Despite the loss, the bout earned Miller his third - and second consecutive -
Fight of the Night bonus. Healy, however, subsequently tested positive for marijuana and the result of the fight was overturned to a No Contest. Miller faced
Fabrício Camões at
UFC 168 in on December 28, 2013. The two were originally scheduled to meet in 2008 at IFL 22 but the bout was scrapped after Camões was forced to withdraw due to injury. Miller locked in an armbar for the submission victory at 3:42 of the first round.
2014 Miller was expected to face
Bobby Green on April 26, 2014, at
UFC 172. However, in the week leading up to the event, Green pulled out of the bout citing an injury and was replaced by
Yancy Medeiros. Miller won the fight via submission in the first round. Miller faced
Donald Cerrone on July 16, 2014, at
UFC Fight Night 45. After a back and forth first round, Miller was defeated via second-round knockout.
2015 Miller was expected to face
Paul Felder on April 18, 2015, at
UFC on Fox 15. However, Felder was forced to pull out of the event due to a knee injury and was replaced by
Beneil Dariush. Miller lost the fight by unanimous decision. Miller faced
Danny Castillo on July 25, 2015, at
UFC on Fox 16, replacing
Rustam Khabilov who was pulled from the card with alleged
visa issues. He won the fight by split decision. Miller faced
Michael Chiesa on December 10, 2015, at
UFC Fight Night 80. He lost the bout via submission in the second round. Despite the loss, Miller was awarded his fourth
Fight of the Night bonus award.
2016 Miller faced
Diego Sanchez on March 5, 2016, at
UFC 196. He lost the fight by unanimous decision. Miller next faced former
Pride FC Lightweight Champion Takanori Gomi on July 9, 2016, at
UFC 200. He won the fight via TKO in the first round. After sustaining virtually no damage during his previous fight, Miller was quickly rescheduled to rematch
Joe Lauzon on August 27, 2016, at
UFC on Fox 21. He won the back-and-forth fight via split decision. The win also earned Miller his fifth
Fight of the Night bonus award. Miller next faced
Thiago Alves on November 12, 2016, at
UFC 205. At the weigh-ins, Alves missed weight by six pounds, weighing in at 162.6 lbs. Miller, who was already on weight, had to rehydrate to keep their weight difference within 7 pounds. Because of that, he came in at 157.6 lbs and the bout proceeded at catchweight.
New York State Athletic Commission and UFC officials indicated that Alves must not weigh more than 173 lbs the day of the fight or the fight would be canceled. As a result, Alves was fined 20% of his fight purse, which went to Miller. He won the fight by unanimous decision.
2017 Miller faced
Dustin Poirier on February 11, 2017, at
UFC 208. He lost the back-and-forth fight by majority decision. Both participants earned
Fight of the Night honors. Miller faced
Anthony Pettis on July 8, 2017, at
UFC 213. He lost the fight by unanimous decision. Miller faced
Anthony Pettis on July 8, 2017, at
UFC 213. He lost the fight by unanimous decision. He lost the fight by unanimous decision.
2018 Miller faced
Dan Hooker on April 21, 2018, at
UFC Fight Night 128. He lost the fight via knockout in the first round. Miller faced
Alex White on September 8, 2018, at
UFC 228. He won the fight via submission in the first round. Miller locked in a rear-naked choke after dropping White with punches. In this bout, Miller subsequently became the first UFC fighter to both reach 30 fights in the organization and win 17 fights in its Lightweight division. Miller faced
Charles Oliveira in a rematch on December 15, 2018, at
UFC on Fox 31. He lost the fight via a rear-naked choke submission early in the first round.
2019 Miller faced
Jason Gonzalez on April 27, 2019, at
UFC Fight Night: Jacaré vs. Hermansson. He won the fight via a rear-naked choke submission in the first round. The win also earned Miller his first
Performance of the Night bonus award. Miller faced
Clay Guida on August 3, 2019, at
UFC on ESPN 5. He won the fight via a technical submission due to a guillotine choke in the first minute of the first round.
2020 Miller faced
Scott Holtzman on February 15, 2020, at
UFC Fight Night 167. He lost the back-and-forth fight by unanimous decision. The bout also earned Miller his seventh
Fight of the Night bonus award. Miller faced to
Roosevelt Roberts on June 20, 2020, at
UFC Fight Night: Blaydes vs. Volkov. He won the fight via verbal submission due to an armbar at 2:25 of the first round. This win earned him the
Performance of the Night award. Miller faced
Vinc Pichel at
UFC 252 on August 15, 2020. He lost the fight by unanimous decision.
2021 Miller was expected to face
Bobby Green on February 13, 2021, at
UFC 258. However the fight was cancelled when Green collapsed after the weigh-ins. Miller faced
Joe Solecki on April 10, 2021, at
UFC on ABC 2. He lost the fight by unanimous decision. Miller was scheduled to face Nikolas Motta on September 18, 2021, at
UFC Fight Night 192. However, a week before the event, Miller
tested positive for COVID-19 and was pulled from the event. This marked the first time Miller pulled out of a fight in his then 49-fight career. Miller faced Erick Gonzalez on October 16, 2021
UFC Fight Night 195. He won the fight via knockout early in round two. This win earned him the
Performance of the Night award.
2022 The bout between Miller and Nikolas Motta eventually took place at
UFC Fight Night 201 on February 19, 2022. Miller won the fight via TKO in the second round. With this win, Miller tied
Donald Cerrone for the most wins in UFC history with twenty-three (23). A week before the event, Green was forced to pull out of the bout and Miller was instead booked at welterweight in a rematch against
Donald Cerrone. Miller won the fight in the second round after submitting Cerrone with a guillotine choke. With this win Miller set the record for the most wins in UFC history.
2023 Miller was scheduled to face
Gabriel Benítez on February 18, 2023, at
UFC Fight Night 219. However, Benítez withdrew due to an undisclosed reason and was replaced by
Alexander Hernandez. He lost the fight via unanimous decision. Miller was scheduled to face
Ľudovít Klein on June 3, 2023, at
UFC on ESPN 46. However, Klein pulled out on May 19 due to illness and was replaced by
Jared Gordon. In turn, Gordon was pulled from the bout on the week of the event after not being medically cleared and was replaced by promotional newcomer Jesse Butler. Miller won the fight by knockout 23 seconds into the first round, thus extending his winning record to 25 wins. The win also earned Miller his fourth
Performance of the Night bonus award.
2024 Miller faced
Gabriel Benítez on January 13, 2024, at
UFC Fight Night 234, and won his 26th UFC bout in the third round by face crank submission, which extended the UFC record for most wins. This fight earned him another
Performance of the Night award. Miller faced
King Green on April 13, 2024, at
UFC 300. He lost the fight via unanimous decision. With this bout, Miller became the only UFC fighter to have fought on
UFC 100,
UFC 200 and
UFC 300. Miller faced
Damon Jackson on November 16, 2024, at
UFC 309. He won his 27th UFC bout in the first round by guillotine choke submission, further extending the UFC record for most wins.
2025 Miller faced
Chase Hooper on April 12, 2025 at
UFC 314. He lost the fight by unanimous decision.
2026 Miller is scheduled to face
Jared Gordon on May 9, 2026 at
UFC 328. ==Personal life==