In the wake of Hurricane Harvey, Watt raised more than $37 million for relief efforts.
"I've been fortunate to be on this stage and to win Defensive Player of the Year awards, but everything that you do on the field pales in comparison to what you do off the field," Watt said. "And at the end of my life, if I'm remembered as a football player and a good football player and that's all I'm remembered for, then I did a poor job in my life. When I go to my grave I want to be remembered as a guy who helped people out and who tried to do as much as he could off the field to be the best man he could be. I'm trying to make my family proud and my fans proud, and go out there and just be the best person I can be and leave the world a little bit better."
Watt was one of three finalists for the award.
The Walter Payton NFL Man of the Year Award recognizes an NFL player for his excellence on and off the field.
Watt is in his seventh NFL season and has been named to the Pro Bowl four times.
The Associated Press contributed to this story.