Although mixed martial arts (MMA) has been around for decades in other countries such as Brazil, it is still a relatively new sport for most of the world. Research on combative sport athletes has focused primarily on the various individual sports that compose MMA such as judo, boxing, and wrestling. To date, there is limited peer-reviewed research investigating professional mixed martial artists. More specifically, there is very limited information regarding the dietary supplement habits of current professional mixed martial arts fighters. Thus, the purpose of this study was to investigate various dietary habits, beliefs, and nutritional supplement usage, in professional mixed martial artists.