Following two Dave Schultz Memorial International Greco-Roman titles in 2000 (85 kg) and 2001 (97 kg), Sonnen transitioned fully to professional fighting, competing across promotions such as Pancrase and World Extreme Cagefighting (WEC). He made his UFC debut at UFC 55 in 2005, followed by his Bodog Fight debut in 2006. Sonnen quickly rose through the ranks, challenging for the WEC Middleweight Championship in 2007 before returning to the Ultimate Fighting Championship in 2009. In the UFC, Sonnen became a prominent challenger, notably vying for both the UFC Light Heavyweight and Middleweight Championships.
In recognition of his impactful career and a legendary rivalry, Chael Sonnen was inducted into the UFC Hall of Fame in 2024 for his seminal UFC 117 fight against Anderson Silva. Beyond the octagon, Sonnen has expanded his presence in combat sports media. In 2024, he also participated in an exhibition boxing bout against Anderson Silva, marking a significant return to competition. Looking ahead, Sonnen is slated to serve as the lead commentator for Real American Freestyle in 2025 and is expected to coach on The Ultimate Fighter: Season 33, further cementing his status as a leading analyst and mentor in the sport.