A professional since 2007, he has fought in the UFC, Bellator, Konfrontacja Sztuk Walki (KSW), Fight Exclusive Night and M-1 Global.

[citation needed] Grabowski defeated Kiril Handzhiyski at FX3 on June 13, 2009 in London (a last-minute replacement for Gary Rawlings).

[2] Damian sustained a shoulder injury during training just a few days before the Overeem fight and had to drop out of both bouts.

Grabowski then returned in 2008 with a first-round armbar win against Dion Staring and then fought in June against Michał Kita to determine the best heavyweight fighter in Poland.

After connecting with a powerful upkick that cut the eyebrow of Kita, who slipped and fell out of the ring, Grabowski was declared the winner by doctor stoppage due to a heavily swollen eye.

Surprised, Grabowski didn't spare the compliments for Tybura after the fight, as the championship belt left in Poland.

His thirteen-fight winning streak was snapped, as he lost the fight via unanimous decision, being unable to stop the takedowns of Konrad, the future winner of the tournament.