Caol Uno is a veteran lightweight fighter. In his brief three-fight return to the UFC in 2009 and 2010, Uno dropped a decision to Spencer Fisher, picked up a draw to debuting prospect Fabricio Camoes and lost a brutal TKO to the much larger lightweight monster Gleison Tibau. He was cut after that fight.
Uno next dropped to featherweight to return to Dream to face off against Kazuyuki Miyata at the year-end Dynamite show. Miyata defeated Uno via dominant unanimous decision. He remained in Dream to face Akiyo Nishiura. He defeated "Wicky" via unanimous decision.
He next faced veteran Takeshi Inoue, losing via highlight-reel first round knockout.
- Hayato Sakurai vs. Caol Uno - The fight was the MMA debut of both men and it was Caol Uno's first loss.
- B.J. Penn vs. Caol Uno 1 - B.J. Penn knocked Uno out within mere seconds in a victory reminiscent of the third round title defense against Sean Sherk years later.
- B.J. Penn vs. Caol Uno 2 - The fight was for the vacant UFC lightweight title which Jens Pulver had vacated. After the fight ended in a draw, the UFC lightweight division became nonexistent for a number of years.
- Tatsuya Kawajiri vs. Caol Uno - The fight was a rare draw.
- Caol Uno vs. Ivan Menjivar - The fight was in the semifinals of the 2006 K1 Hero's lightweight grand prix.
- Caol Uno vs. Gesias Cavalcante - The fight was in the finals of the 2006 K1 Hero's lightweight grand prix.
- Spencer Fisher vs. Caol Uno - The fight was Uno's short-lived return to the UFC. The fight ended in a controversial decision for Spencer Fisher.