Trump often stood closely behind the Democratic nominee glowering as she answered questions from the audience during the town hall-style event in St Louis.
Speaking during an interview on NBC's The Ellen DeGeneres Show set to air Friday, Clinton said his movements made her feel "really weird" on stage.
"Because of the revelation of the public video, and everything that came out on 'Access Hollywood,' you know, he was really all wrought up, and you could just sense how much anger he had," Clinton said, referring to a video leaked last week showing Trump making lewd comments about women.
"And so he was really trying to dominate and then literally stalk me around the stage and I would just feel this presence behind me." Trump rejected criticism about his debate performance at a rally on Monday.
"So I'm standing at my podium by my chair. She walks across the room. She's standing in front of me, right next to me," he said. "And the next day I said what did the papers say? They said, 'he invaded her space.'"
"Believe me," he added, "The last space that I want to invade is her space." Last week's video showed Trump boasting in 2005 of groping women with impunity because he was famous, sending the White House race into unprecedented levels of vulgarity.
Since then, at least six women have accused him of making unwanted physical advances, most of them after Trump asserted in Sunday's debate that he had never sexually assaulted a woman.
During her interview, Clinton praised First Lady Michelle Obama for blasting the Republican nominee in a powerful tirade yesterday. "The speech that she gave, I think, put into words what so many people are feeling," Clinton said.
"And not just women and girls. Men and boys." She also said she didn't notice making a much-commented shimmy motion during Sunday's debate when Trump accused her of not having the "right temperament" to be president. "Now people are always saying, 'Do the shimmy, do the shimmy.'"