Early career Before his professional career, he fought as an amateur. In his last bout, he defeated Michał Pach by a split decision at the TFL 12: Hydro Truck Night event. His first professional fight came four months later, against Wojciech Żuchnik. Bartosiński won again by unanimous decision. After a half-year hiatus, he would return in a bout against Jarosław Lech. Bartosiński would win via TKO in the second round. He would return seven months later against
Ukraine's Vladislav Schepanskyi. He would defeat the latter via a Doctor Stoppage in the first round. Three months later, he would return in a bout against
Russia's Alexander Shingarenko. Bartosiński would win via a first-round TKO.
Fight Exclusive Night Three months later, Bartosiński would fight under Poland's second biggest promotion,
Fight Exclusive Night. He fought Krystian Bielski. Bartosiński would win via TKO, and also earn himself a Knockout of the Night bonus.
Return to regional circuit Two months later, he would return to take on
Ukraine's Konstantin Linnik in his home town of
Rawa Mazowiecka. Bartosiński would win via a first-round TKO.
Konfrontacja Sztuk Walki Tylko Jeden Adrian would compete in the Tylko Jeden tournament. He would compete for a contract with
Konfrontacja Sztuk Walki. In the first round, he faced Kamil Dołgowski, whom he would beat via a Doctor Stoppage in the first round. His next fight in the tournament would be against Piotr Walawski. Bartosiński would win via a third-round TKO, and thus advancing to the finals. Bartosiński was set to face Tomasz Romanowski in the final, however he would suffer an injury, and was forced to withdraw from the tournament.
Main Roster Despite not winning the tournament, Bartosiński would still eventually sign with the promotion. His first fight came almost a year later, when he took on
Spain's Lionel Padilla. Bartosiński would win via a third-round TKO. His next fight would come four months later, where he took on fellow countryman, Michał Michalski. He would beat Michalski via a first-round TKO. After over half a year out, he would return against Andrzej Grzebyk. Bartosiński would win via submission for the first time in his career. This performance would earn him a Submission of the Night bonus. After a nine-month hiatus, he would return to the cage against Krystian Kaszubowski. Bartosiński would win via a first-round TKO.
KSW Welterweight Champion Five months later, he would face Artur Szczepaniak for the vacant
KSW Welterweight Championship. Bartosiński would win the fight via a first-round TKO, and thus claiming his first career championship. In the process, he also received a Knockout of the Night bonus. His first title defense would come eight months later, when he took on
France's
Salahdine Parnasse. Parnasse was also the current
Featherweight and
Lightweight champion. Bartosiński would win the fight via Unanimous Decision. His next title defense came five months later. Bartosiński was originally scheduled to face Andrzej Grzebyk in a rematch, however Grzebyk pulled out due to injury. He would end up facing
Igor Michaliszyn, whom he would beat via submission in the third round. His next fight was not a title fight. He would face veteran fighter
Mamed Khalidov half a year later. Khalidov would win via submission in the second round, and in the process handing Bartosiński his first career loss. Five months later, he would face Andrzej Grzebyk in a rematch. This time the fight being for the title. Bartosiński would win via a Unanimous Decision in what is claimed by many to be the greatest fight in the organization. Bartosiński would also earn himself a Fight of the Night bonus. Following an eight month hiatus after sustaining an injury in his last fight, his fourth title defense came on December 20, 2025, against
Muslim Tulshaev. Bartosiński won the fight via a third-round TKO. This fight earned him his second Fight of the Night bonus. His next title defense came on March 14, 2026, against Madars Fleminas. Bartosiński won the fight via a controversial Split Decision, defending his title successfully for the fifth time. ==Championships and accomplishments==