A video clip that made the rounds online shows Wade shooting jump shots while warming up with forward Amar'e Stoudemire during the performance of "O Canada" ahead of Game 3 at American Airlines Arena in Miami.
The Heat lost 95-91; Wade scored a game-high 38 points.
On Sunday, Wade defended his actions, but he didn't exactly apologize.
"It's something that I do before every game that I prepare for, and I've been doing it my whole career," said the Heat's star guard. "So I understand whatever is said from that standpoint, but I'm not a disrespectful person. So if anybody thinks I'm being disrespectful towards a country, then they have no idea of who Dwyane Wade is."
Wade said the situation came down to timing, explaining that Saturday's team pregame routine started a little bit later than compared to when the Heat were in Toronto for Games 1 and 2.
"It was no disrespect from myself or Amar'e or anybody," Wade said. "And if anybody feels like it was, please don't fill up my timeline with disrespectful comments because that's not this guy right here. Find somebody else for that. But we'll adjust our pregame routine for the next game."
Toronto Mayor John Tory fired back on Twitter, directing a tweet toward Wade saying "a Canadian invented the game," referring to James Naismith. "Respect the anthem."
Ryan Wolstat of the Toronto Sun added, "Not a fan of anthems before games but will say if a Canadian did what Wade did yesterday for the other anthem, there'd be huge outrage."
Meanwhile, Associated Press sportswriter Tim Reynolds, who tweeted that Wade has done this before during the "Star Spangled Banner," had a different take, saying rather than being disrespectful, Wade was just trying to make one final shot in warmups.
Technically, what Wade did was against NBA rules. From the NBA rule book: "Players, coaches and trainers are to stand and line up in a dignified posture along the sidelines or on the foul line during the playing of the National Anthem."
CNN reached out to the NBA to see if the league would reprimand Wade or the Heat.