Hathaway, 36, told Ellen DeGeneres that while she filmed the 2019 thriller Serenity with the hunk, they went out for a tour of Mauritius island's best rum bars.
"How was that?" asked DeGeneres, 60.
"I don't remember," admitted Hathaway, adding that she cannot hold alcohol as well as McConaughey, 49, and his wife, Camila Alves.
"We drank the night away, and then I had to go to a meeting with Steven Knight, our director, the next day," she continued, saying that she stumbled into the room with one eye open and feeling lousy.
"You quit drinking after that, right?" asked the show host, after which Hathaway admitted she gave up booze in October of 2018.
"I'm going to stop drinking while my son is living in my house, just because I don't totally love the way I do it and he's getting to an age where he really does need me all the time in the morning," she said.
Hathaway explained that her night out with McConaughey wasn't the only thing that made her decide to swear off cocktails for the next 18 years.
"I did one school run one day where I dropped him off at school, I wasn't driving, but I was hung over and that was enough for me," said the actress. "I didn't love that one."
"Yeah, that's another reason I don't want kids," joked DeGeneres.
RadarOnline.com readers know Hathaway is a mother to 2-year-old son Jonathan, whom he shares with husband Adam Shulman.
And while being a mom is the main reason Hathaway decided to quit drinking, this is not the first time she's spoken of her questionable alcohol habits.
"It's never gotten in the way of me being able to do the work, but I think it was approaching an unhealthy level," the star said in a 2017 interview with ABC.
At the time, she also admitted that while she loved boozing as a teen, her drinking began to increase as she advanced in her career.
"I went to college and I drank a great deal," she said. "By the time of The Devil Wears Prada I was drinking more."
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