He interrupted his speech at a campaign stop in South Carolina to tell the 1,800 in attendance that his trademark hairdo is for real.
"I don't wear a toupee, it's my hair, I swear," he said.
The billionaire developer waved a copy of The New York Times shortly after taking the stage, saying the newspaper accused him of wearing a toupee.
Trump even brought a woman out of the audience to take a closer look and told her to tug on his hair.
Then he called a woman onstage from a front table and instructed her to tug on his hair.
As she pulled, he asked her to confirm that it's real. She said, "I do believe it is," to laughter and applause, and Trump tossed his copy of the Times into the crowd.
Trump leads most polls of GOP primary voters.
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The Associated Press contributed to this report.