Alec Baldwin is said to be "smitten" with a 28-year-old yoga instructor.
The 52-year-old star has been spotted at parties and photographed with Hilaria Thomas - a New York University graduate - with their most recent public outing at Carnegie Hall's 120th anniversary afterparty last month.
A source told the New York Post newspaper: "He's really into her. He's taking her to the Tony awards."
The '30 Rock' actor appears to have changed his attitude since last year, when he ruled out romancing any younger women.
He said: "What's worse than waking up with a 25-year-old woman, you know what I mean? You want to go shoot yourself because you have nothing to say to her. Seriously.
"It's sad but there are men who go for whatever their earliest ideal of a sexual partner was, they stay with that ideal, meaning men often lock into the image of the first girl they loved at 18. They get stuck in an idea of sexuality with young women. Other men learn to see beyond all that."
A spokesperson for Alec - who is currently shooting new movie 'Rock of Ages' with Russell Brand and Tom Cruise - was more open about his present relationship status, joking: "He's actually been dating Russell Brand down in South Florida."
Alec was previously married to actress Kim Basinger from 1993 to 2001. They have one daughter together, Ireland, 15.
Since his split from Kim, Alec has been linked to a string of beautiful women, including actress Kristin Davis, lawyer Nicole Seidel and reality TV star Johanna Cox, and has said he would eventually like to have another wife.
He said: "I would love to marry again. I want to be in love again. I was in love when I was married, I'm not ashamed to say. I used to wake up in the morning and just look at Kim and say, 'What do you want for breakfast, baby? Special K with blueberries? Let me go get some.' "