Early career

Uno finished second in the All Japan amateur Shooto tournament in 1996.^[3] He was a runner-up in the submission wrestling world championships at ADCC losing in the finals to world-renowned Jean Jacques Machado.

Shooto

Uno rose through the ranks of the Shooto mixed martial arts organization in Japan. In May 1999, Uno fought the then-legendary Rumina Sato. The fight was hailed as "Fight of the Year", an extremely fast-paced back and forth battle with a wide variety of stand-up and grappling exchanges.^{[citation needed]} Eventually, Uno took the back of Sato and choked him into submission.

The two rematched in December 2000. This fight concluded with Uno standing over Sato on his back, then striking him with a knee and a punch while he was getting up, knocking him out.

UFC

After his second victory over Rumina Sato, Uno was recruited to fight for the UFC's Bantamweight (later renamed Lightweight) title against Jens Pulver. Throughout the fight, Pulver stopped Uno's takedown attempts and pressed the action on the feet. Uno, who had earned a reputation as being "unflappable", began to show frustration for the first time in his career as Pulver neutralized all his offensive efforts.^{[citation needed]} Pulver took a majority decision win in the fight.

After Pulver left the UFC, the Lightweight Championship was vacated. A tournament was put together pitting the top Lightweights in the UFC (B.J. Penn, Din Thomas, Matt Serra and Caol Uno). In the first round, Uno faced Thomas. Thomas dominated the first round, setting a high pace. However, Uno turned things around, taking the second and third rounds to win the fight.

In the finals of the tournament, Uno faced Penn (who had previously defeated Uno by knockout in under 12 seconds). Uno used angles and effective wrestling techniques to frustrate Penn, who appeared tentative from the start, while Penn was dominant in spurts. The fight was called a draw and neither fighter won the championship belt.

Return to Japan

Uno then went on to fight Tatsuya Kawajiri in Shooto before fighting at K-1's 2004 Premium Dynamite!! and K-1 MAX: Japan Grand Prix 2005. His next eleven fights were for the then newly established promotion Hero's.

Uno next competed in DREAM's Lightweight Grand Prix. He was seeded directly into the second round, DREAM 3, where he beat Mitsuhiro Ishida via rear-naked choke submission to progress to the Dream 5: Lightweight Grand Prix 2008 Final Round. At Dream 5, Uno lost a unanimous decision to Shinya Aoki.

UFC return

Uno was spotted in attendance at UFC 94, fueling talk of a return to the UFC's Lightweight division. It was later confirmed that Uno had signed with the UFC and would face Spencer Fisher at UFC 99: The Comeback. In spite of finishing the bout pounding Fisher with punches from top crucifix position, Uno lost by a controversial unanimous decision. Then, on November 21, 2009, Uno fought UFC newcomer Fabrício Camões to a majority draw at UFC 106.

On March 31, 2010, Uno fought Gleison Tibau at UFC Fight Night 21. He was overpowered by the much bigger Tibau, and suffered a loss via TKO (punches).^[4] After the fight he was released from the promotion.

Post-UFC career

After parting ways with the UFC, the fighter's trajectory in the Japanese MMA circuit was marked by a diverse range of outcomes. Following his featherweight debut in Dynamite!! 2010, where he faced a unanimous decision loss against Kazuyuki Miyata, he rebounded with a victory over Akiyo Nishiura at Dream: Fight for Japan! in May 2011. However, a notable setback occurred in September 2011 when he suffered a knockout defeat due to a head kick from Takeshi Inoue at DREAM 17.

Undeterred, he demonstrated resilience in subsequent matches, securing wins via submission over opponents such as Kyu Hwa Kim, Anthony Avila, and Daniel Romero in 2013. The trend continued with victories against Jesse Brock,^[5] Taiki Tsuchiya, and Raja Shippen in 2014..^[6] Despite facing challenges and a decision loss to Yoshifumi Nakamura in January 2015, he rebounded with a submission win against Jung Ho Hwang in April 2016.

The fighter continued to navigate the competitive landscape, experiencing both victories and defeats. Notable moments include a submission win over Markus Held in November 2019 and a KO loss to Taison Naito in May 2021. The journey reached its recent chapter with decision losses to Akira Haraguchi in November 2021 and a knockout defeat to Shota Takagi at Shooto 2023 Vol.7 in November 2023.^[7]

All Japan Pro Wrestling (2002–2003)

Uno then signed up with All Japan Pro Wrestling in June 2002, where he debuted as a partner for Kendo Kashin against Kaz Hayashi and Kashin's double Mr. Problem (played again by Matsui), albeit in another losing effort. In November, he became also part of the event Wrestle-1, co-promoted with K-1. Coming under a monkey mask (which he quickly lost) and the name "The Apeman Nigo", Uno teamed up with Kashin to defeat La Parka and Super Parka.^[8]

He returned to AJPW in May 2003 under his Apeman Nigo persona. He and Kaz Hayashi lost to Kashin and Low Ki, but at the next event he teamed up with Ki to beat Gran Naniwa and Ryuji Hijikata. At the next day, he competed under his true name with Keiji Mutoh, winning over 728% Machine and The Apeman 200%, and then recovered his Nigo mask to team with Mutoh and Taka Michinoku in a winning effort against The Great Sasuke, The Great Kosuke and The Apeman. Uno's last appearance for AJPW would be in July, allying with Kashin and Robbie Brookside to beat Hayashi, Jimmy Yang and Ebessan.

Mixed martial arts

• All Japan Amateur Shooto
  • All Japan Amateur Shooto Tournament Runner-up (1996)
• Ultimate Fighting Championship
  • UFC 41 Lightweight Tournament Co-Champion (drew with B.J. Penn in the finale)
• Shooto
  • Shooto Lightweight Championship (One Time)
  • One successful title defense vs. Rumina Sato
• K-1 Hero's
  • 2007 K-1 HERO'S Lightweight Tournament Semifinalist
  • 2006 K-1 HERO'S Lightweight Tournament Runner Up
  • 2005 K-1 HERO'S Lightweight Tournament Semifinalist
• DREAM
  • 2008 DREAM Lightweight Grand Prix Semifinalist

Submission wrestling

• ADCC Submission Wrestling World Championship
  • ADCC Submission Wrestling World Championship Silver Medalist 66k-76k (1999)