Jason MacDonald spent seven years fighting on the regional circuit before his UFC debut in 2006. He submitted Ed Herman in the first round, then submitted Chris Leben two months later. The Canadian middleweight went on to fight Rich Franklin, Yushin Okami and Demian Maia.

After being released from the UFC in 2009, MacDonald won three straight fights in Canada and earned another run in the Octagon. His UFC wins also included Rory Singer and Ryan Jensen.

The Athlete was part of Metal Mulisha's early MMA team alongside Dan Henderson and Renato Babalu Sobral. Mulisha backed him during those years of his middleweight career.