Souwer started kickboxing when he was 7 years old at Ling Ho Gym in Baku. He had his first kickboxing fight when he was 8 years old. He won all his fights, in all the weight classes he fought and became Dutch Champion. In 1998, only 16 years old, Souwer fought his first A-Class MTBN Title match, which he won on points. When he was 18 he had three different World titles. Souwer first went to Japan in 2002 to compete in the S-Cup 2002shoot boxing competition where he became the winner after defeating Chinese sanshou title challenger Zheng Yuhao. He made his K-1 debut the next year and won his first K-1 World Max champion title in 2005. Andy Souwer is the 2007 K-1 World Max Champion. He defeated Gago Drago followed by Albert Kraus and finally Masato to win the championship. He faced Masato again in Masato's retirement match at the Dynamite!! 2009 event, and lost. He was scheduled to face Naruepol Fairtex at Fighterzone Kickboxing World Series MAX in Singapore on February 25, 2012. However, they were not paid by the promoter and the fight did not happen. He won the Shoot Boxing World Tournament 2012 in Tokyo, Japan on November 17, 2012 After beating Kem Sitsongpeenong by majority decision at the quarter-final stage and knocking outHiroki Shishido in the semis, he defeated stablemate and student Henri van Opstal by unanimous decision in the final. At the K-1 World MAX 2012 World Championship Tournament Final in Athens, Greece on December 15, 2012, Souwer outpointed Andy Ristie in the quarter-finals before losing a unanimous decision to Artur Kyshenko in the semis, in what was the fourth fight of their rivalry. He lost to Dzhabar Askerov by split decision in the main event of Yokkao Extreme 2013 in Milan, Italy on January 26, 2013. Souwer led a team of shoot boxers against a team of Pancrase fighters at Shoot Boxing 2013 - Act 4 on June 23, 2013. There was some controversy leading up to the event, with Souwer saying of the Pancrase representatives "in Holland, they are what we call B level fighters" and Shoot Boxing founder and president Caesar Takeshi storming out of a pre-fight press conference, apparently so upset at Pancrase's disrespectful selection of opponents that he could no longer bear to be a part of the proceedings. Souwer knocked out his opponent, Kota Okazawa, with a left hook in round one. Souwer was scheduled to fight Maximo Suarez at Enfusion Live: Tenerife in Tenerife, Spain on July 13, 2013 but withdrew for undisclosed reasons. He took a unanimous decision over Yasuhiro Kido at the K-1 World MAX 2013 World Championship Tournament Final 16 in Mallorca, Spain on September 14, 2013. He defeated Steve Moxon by unanimous decision at Shoot Boxing Battle Summit Ground Zero Tokyo 2013 in Tokyo, Japan on November 15, 2013. He was scheduled to fight Enriko Kehl at the K-1 World MAX 2013 World Championship Tournament Quarter Finals - Part 1 in Foshan, China on December 28, 2013. However, he was unable to compete after suffering from a bout of appendicitis in the weeks prior to the event which forced him into hospital where they had to perform a routine but emergency surgical procedure to remove the troubled organ. His opponent, Kehl, was also unable to fight on the card after suffering numerous cuts in a fight with Buakaw earlier that month and was moved to K-1 World MAX 2013 World Championship Tournament Quarter Finals - Part 2 and matched with Shane Campbell. Andy Souwer and Shemsi Beqiri were set to fight at SuperPro Fight Night VI in Basel. Switzerland on January 25, 2014 but Souwer withdrew due to his bout of appendicitis and was replaced by Foad Sadeghi. He lost a split decision to Tsukuru Midorikawa at Rikix: No Kick, No Life 2014 in Tokyo, Japan on February 11, 2014. Souwer made his professional boxing debut on March 17, 2014, winning by TKO after his opponent Paata Varduashvili retired in his corner at the end of the fourth round in Den Bosch, Netherlands. He defeated Yuri Bessmertny via UD at Legend 3: Pour Homme in Milan, Italy on April 5, 2014.
