Noah was angry after picking up his second foul with 6:26 left in the first quarter. After sitting down on the bench he turned to his right and shouted toward a fan.
"I apologize," Noah said. "The fan said something to me that I thought was disrespectful, and I got caught up in the moment, and I said some things that I shouldn't have said. I was frustrated and I don't mean no disrespect to anybody. I just got caught up."
Noah said he expects to be fined for the comment.
NBA spokesman Tim Frank declined to comment on the incident.
"While I'm fully aware that basketball is an emotional game, such a distasteful term should never be tolerated," Commissioner David Stern said in a statement. "Accordingly, I have fined Kobe $100,000. Kobe and everyone associated with the NBA know that insensitive or derogatory comments are not acceptable and have no place in our game or society."
The Gay and Lesbian Alliance Against Defamation (GLAAD) issued a statement Monday.
"Last month the NBA sent an important message about how such slurs fuel a climate of intolerance and are unacceptable," GLAAD president Jarrett Barrios said. "These anti-gay remarks, coming so soon after, demonstrate how much needs to be done.
"Noah's apology is a start. We are confident that the NBA will now take disciplinary measures and hasten its work with us to tell all players that there is no place for anti-gay words and attitudes in the game."
Noah scored just one point to go along with five rebounds Sunday and struggled defensively against the Heat's Chris Bosh, who had 34 points as Miami went up 2-1 in the series.
Nick Friedell covers the Bulls for ESPNChicago.com and ESPN 1000.