Submission Underground 28 took place Sunday, October 31, 2021 with 10 fights in Portland, Oregon.

Submission Underground returns to Portland, Oregon with an eight-man absolute tournament featuring some of the top submission-only grapplers and jiu-jitsu players in the world. The winner of the whole tournament will receive a handsome cheque of $10,000 and a title shot at the champion Mason Fowler on July 18th. 2nd place will receive $5000 whilst 3rd place will receive $2500.