The mouthguard ended up hitting Andrew Forbes, the son of Cavaliers minority owner Nate Forbes, who was sitting in the front row.
The two shook hands and Curry immediately apologized.
Forbes spoke to fellow spectator and tech host Gary Vaynerchuk about what was said after the errant throw.
"His mouthpiece hit me in the face and he was actually very polite," he said.
The Cavs won 115-101, forcing Game 7 on Sunday at Oracle Orena in Oakland, California.
"I've thrown my mouthpiece before. I usually aim at the scorer's table. I was off aim. Definitely didn't mean to throw it at a fan," Curry said after the game, according to ESPN.
Curry was ejected from the game after throwing the mouthguard.
Forbes also spoke to ESPN about the incident last night.
"It's all good," Forbes said. "It just hit me, and I was like, 'Who? What?' I was just cheering, being a fan. I don't even know where he was throwing it...he was good about it."
Here's the throw.