In an interview with Vogue published Wednesday, the magazine's November cover star was asked if she turned down the Super Bowl halftime show in solidarity with Kaepernick, a former NFL quarterback who became the first player to protest social inequality and police brutality during the national anthem.
"Absolutely," the singer said. "I couldn't dare do that. For what? Who gains from that? Not my people. I just couldn't be a sellout. I couldn't be an enabler.
"There's things within that organization that I do not agree with at all, and I was not about to go and be of service to them in any way."
Kaepernick hasn't appeared in an NFL game since the 2016 season, when he began to kneel during the national anthem to raise awareness for social issues.
The quarterback filed a grievance against the league in October 2017 that accused team owners of colluding to keep him out of the NFL. The sides reached a settlement in February.
Instead of Rihanna, the NFL had Maroon 5 and rapper Travis Scott perform at halftime. During this year's Super Bowl halftime performance, the league is teaming up with Jay-Z's Roc Nation, which is helping produce the show starring Jennifer Lopez and Shakira.