Trump also claimed to not be a fan of the Vietnam War.
At a press conference later, the Associated Press reports that Trump tried to clarify his remarks, saying, "If a person is captured, they're a hero as far as I'm concerned. I don't like the job John McCain is doing in the Senate because he is not taking care of our veterans."
Trump also posted a clarification on his official Twitter account.
Other Republican presidential candidates were quick to react on social media, lambasting Trump for his comments on McCain.
Former Republican presidential candidate Mitt Romney offered his opinion.
McCain's daughter also took to Twitter to offer her reaction to Trump's remarks.