| Res. | Record | Opponent | Method | Event | Date | Round | Time | Location | Notes |
| Loss | 26–10 (2) | Robbie Lawler | TKO (retirement) | UFC 266 | September 25, 2021 | 3 | 0:44 | Las Vegas, Nevada, United States | |
| NC | 26–9 (2) | Anderson Silva | NC (overturned by NSAC) | UFC 183 | January 31, 2015 | 5 | 5:00 | Las Vegas, Nevada, United States | Middleweight debut. Originally a unanimous decision win for Silva; overturned after he tested positive for drostanolone and androsterone. Diaz also tested positive for elevated marijuana metabolites. |
| Loss | 26–9 (1) | Georges St-Pierre | Decision (unanimous) | UFC 158 | March 16, 2013 | 5 | 5:00 | Montreal, Quebec, Canada | For the UFC Welterweight Championship. |
| Loss | 26–8 (1) | Carlos Condit | Decision (unanimous) | UFC 143 | February 4, 2012 | 5 | 5:00 | Las Vegas, Nevada, United States | For the interim UFC Welterweight Championship. Diaz tested positive for marijuana. |
| Win | 26–7 (1) | Penn | Decision (unanimous) | UFC 137 | October 29, 2011 | 3 | 5:00 | Las Vegas, Nevada, United States | Fight of the Night. |
| Win | 25–7 (1) | Paul Daley | TKO (punches) | Strikeforce: Diaz vs. Daley | April 9, 2011 | 1 | 4:57 | San Diego, California, United States | Defended the Strikeforce Welterweight Championship. Diaz vacated the title on June 9, 2011 when his contract was absorbed by the UFC. |
| Win | 24–7 (1) | Evangelista Santos | Submission (armbar) | Strikeforce: Diaz vs. Cyborg | January 29, 2011 | 2 | 4:50 | San Jose, California, United States | Defended the Strikeforce Welterweight Championship. |
| Win | 23–7 (1) | K. J. Noons | Decision (unanimous) | Strikeforce: Diaz vs. Noons II | October 9, 2010 | 5 | 5:00 | San Jose, California United States | Defended the Strikeforce Welterweight Championship. |
| Win | 22–7 (1) | Hayato Sakurai | Submission (armbar) | Dream 14 | May 29, 2010 | 1 | 3:54 | Saitama, Japan | |
| Win | 21–7 (1) | Marius Žaromskis | TKO (punches) | Strikeforce: Miami | January 30, 2010 | 1 | 4:35 | Sunrise, Florida, United States | Won the inaugural Strikeforce Welterweight Championship. |
| Win | 20–7 (1) | Scott Smith | Submission (rear-naked choke) | Strikeforce: Lawler vs. Shields | June 6, 2009 | 3 | 1:41 | St. Louis, Missouri, United States | Catchweight (180 lb) bout. |
| Win | 19–7 (1) | Frank Shamrock | TKO (punches) | Strikeforce: Shamrock vs. Diaz | April 11, 2009 | 2 | 3:57 | San Jose, California, United States | Catchweight (180 lb) bout. |
| Win | 18–7 (1) | Thomas Denny | TKO (punches) | EliteXC: Unfinished Business | July 26, 2008 | 2 | 0:30 | Stockton, California, United States | Lightweight bout. |
| Win | 17–7 (1) | Muhsin Corbbrey | TKO (punches) | EliteXC: Return of the King | June 14, 2008 | 3 | 3:59 | Honolulu, Hawaii, United States | |
| Win | 16–7 (1) | Katsuya Inoue | TKO (corner stoppage) | Dream 3 | May 11, 2008 | 1 | 6:45 | Saitama, Japan | Return to Welterweight. |
| Loss | 15–7 (1) | K. J. Noons | TKO (doctor stoppage) | EliteXC: Renegade | November 10, 2007 | 1 | 5:00 | Corpus Christi, Texas, United States | For the inaugural EliteXC Lightweight Championship. |
| Win | 15–6 (1) | Mike Aina | Decision (split) | EliteXC: Uprising | September 15, 2007 | 3 | 5:00 | Honolulu, Hawaii, United States | |
| NC | 14–6 (1) | Takanori Gomi | NC (overturned by NSAC) | PRIDE 33 | February 24, 2007 | 2 | 1:46 | Las Vegas, Nevada, United States | Return to Lightweight. Originally a submission (gogoplata) win for Diaz; overturned after he tested positive for marijuana. |
| Win | 14–6 | Gleison Tibau | TKO (punches) | UFC 65 | November 18, 2006 | 2 | 2:27 | Sacramento, California, United States | |
| Win | 13–6 | Josh Neer | Submission (kimura) | UFC 62 | August 26, 2006 | 3 | 1:42 | Las Vegas, Nevada, United States | Submission of the Night. |
| Win | 12–6 | Ray Steinbeiss | Decision (unanimous) | International Cage Fighting Organization 1 | May 13, 2006 | 3 | 5:00 | Stockton, California, United States | |
| Loss | 11–6 | Sean Sherk | Decision (unanimous) | UFC 59 | April 15, 2006 | 3 | 5:00 | Anaheim, California, United States | |
| Loss | 11–5 | Joe Riggs | Decision (unanimous) | UFC 57 | February 4, 2006 | 3 | 5:00 | Las Vegas, Nevada, United States | |
| Loss | 11–4 | Diego Sanchez | Decision (unanimous) | The Ultimate Fighter 2 Finale | November 5, 2005 | 3 | 5:00 | Las Vegas, Nevada, United States | |
| Win | 11–3 | Koji Oishi | KO (punches) | UFC 53 | June 4, 2005 | 1 | 1:24 | Atlantic City, New Jersey, United States | |
| Win | 10–3 | Drew Fickett | TKO (punches) | UFC 51 | February 5, 2005 | 1 | 4:40 | Las Vegas, Nevada, United States | |
| Loss | 9–3 | Karo Parisyan | Decision (split) | UFC 49 | August 21, 2004 | 3 | 5:00 | Las Vegas, Nevada, United States | |
| Win | 9–2 | Robbie Lawler | KO (punch) | UFC 47 | April 2, 2004 | 2 | 1:31 | Las Vegas, Nevada, United States | |
| Win | 8–2 | Jeremy Jackson | Submission (armbar) | UFC 44 | September 26, 2003 | 3 | 2:04 | Las Vegas, Nevada, United States | |
| Win | 7–2 | Jeremy Jackson | TKO (punches) | IFC Warriors Challenge 18 | July 19, 2003 | 1 | 4:33 | Lakeport, California, United States | |
| Win | 6–2 | Joe Hurley | Submission (kimura) | WEC 6 | March 27, 2003 | 1 | 1:55 | Lemoore, California, United States | Won the inaugural WEC Welterweight Championship. Diaz vacated the title to focus on fight for the UFC. |
| Loss | 5–2 | Kuniyoshi Hironaka | Decision (split) | Shooto: Year End Show 2002 | December 14, 2002 | 3 | 5:00 | Chiba, Japan | |
| Win | 5–1 | Harris Sarmiento | TKO (corner stoppage) | Warriors Quest 8 | October 24, 2002 | 2 | 1:47 | Honolulu, Hawaii, United States | |
| Loss | 4–1 | Jeremy Jackson | TKO (punches) | Ultimate Athlete 4: King of the Mountain | September 28, 2002 | 1 | 0:49 | Auberry, California, United States | Ultimate Athlete Welterweight Tournament Final. |
| Win | 4–0 | Adam Lynn | Submission (armbar) | 1 | 2:51 | Ultimate Athlete Welterweight Tournament Semifinal. |
| Win | 3–0 | Blaine Tyler | TKO (punches) | 2 | 2:01 | Ultimate Athlete Welterweight Tournament Quarterfinal. |
| Win | 2–0 | Chris Lytle | Decision (unanimous) | IFC Warriors Challenge 17 | July 12, 2002 | 3 | 5:00 | Porterville, California, United States | Welterweight debut. Won the IFC United States Welterweight Championship. |
| Win | 1–0 | Mike Wick | Submission (triangle choke) | IFC Warriors Challenge 15 | August 31, 2001 | 1 | 3:43 | Oroville, California, United States | Lightweight debut. |