Frank began training for Pancrase, in 1994 and learned the art of submission fighting. In December 1994, Frank made his debut. Frank’s performance dwindled later even though he performed well in the Pancrase organization.

In 1997, Frank Shamrock started fighting in the UFC and fought the unbeaten Kevin Jackson for the UFC lightweight title. By making Kevin submit in just 22 seconds, he shocked everyone to take the title for him. Against many opponents, Frank successfully defended his title, including one with John Lober, from whom he had previously lost.

For Frank, fighting John Lober was personal, as John had stirred up emotions by sending dirty emails and bad mouthing him. In seven minutes, Frank Shamrock defeated John Lober and gained a satisfied victory. Frank Shamrock fought Tito Ortiz to defend his title in 1998. The match an extraordinary one and Frank ended by pummeling his opponents head with punches. After this fight, Frank Shamrock retired from the UFC.

After coming out of retirement, he defeated Elivis Sinosic in 2000. Over former student Shannon Ritch, he won a kickboxing match. Again, in 2003, he came back to MMA betting to defeat Bryan Pardoe by submission. Currently as a special guest, Frank Shamrock pops up in the odd fight. He even trains new up and coming fighters in the sport.

At Superbrawl in Hawaii, in his first sanctioned mixed martial arts match, his opponent was Jon Hess. Belfort defeated him in 12 seconds by knockout (KO). The Phenom was the nickname given when he moved on to compete in the UFC. Inside the octagon, he became the youngest fighter ever to score a victory.

In a rematch, Belfort defeated Couture but lost in their third and final match. In the UFC, he fought against his training partner Joe Charles and via armbar defeated him. Future Pride Middleweight champion Wanderlei Silva, was also defeated in just 44 seconds by TKOing. He started to train with Brazilian Top Team and stopped training with Carlson Gracie. In Pride, he fought five more times against Heath Herring, Daijiro Matsui, Bobby Southworth, Gilbert Yvel and Yoshiki Takahashi. He sustained an injury prior to a fight against Tito Ortiz in the main event of UFC’s first Las Vegas show at UFC 33. Belfort eventually returned, fought and won Marvin Eastman. He lost to Chuck Liddell via decision. On February 2, 2004, against Randy Couture he won it in 49 seconds. On February 5, 2005, against Tito Ortiz, Belfort was impressive but he lost the match by split decision. In his pro boxing debut, Belfort fought against Josemario Neves, on April 11, 2006 and won by TKO.

On October 21, 2006, Belfort tested positive for an illegal substance, 4-hydroxytestosterone and was suspended for nine months from the date of the hearing and fined $10,000 on December 21, 2006.

On April 21, 2007, Vitor Belfort defeated Ivan Serati by TKO at Cage Rage 21. At Cage Rage 23, he defeated James Zikic. In November of 2010, for the Middleweight title, Belfort will challenge the winner of the Anderson Silva-Chael Sonnen fight.