The former "Prison Break" star revealed his sexual identity last month in a letter posted on the Gay & Lesbian Alliance Against Defamation website.
TMZ said Miller talked at Saturday night's Human Rights Campaign Dinner about attempting suicide for the first time when he was 15 because he didn't know how to express who he was.
He recalled swallowing a bottle of pills at home and said the action wasn't a cry for help.
"You only cry for help if there is help to cry for," TMZ quoted the 41-year-old actor as saying.
Miller said he hopes that by now being truthful about who he is he can be a role model for other gay actors in Hollywood.
"To be the someone else that no one was to me," he said.
Moore to attend retreat in to avoid Kutcher's wedding
Yosemite climber falls 30 feet, suffers major injuries