The One Day actress, who has been in a relationship with Adam Shulman for three years, admitted that she is now open to the institution after seeing how happy it can make people.
Hathaway told Interview: "I am open to marriage, actually. I just went through a phase where I wanted to look at it from every angle to make sure that I wasn't just falling in step with some kind of prescribed fantasy.
"I was at my best friend's wedding just two days ago, and I watched this person who I love like a sister, and who has changed my life and continues to change my life for the better, who I feel as close to as I do my family, commit herself to a man who she loves, and I watched how happy it made her.
"I mean, she looked like she was riding a bubble the whole night. I thought, 'Weddings are important because they celebrate life and possibility'."
The 28-year-old said that her change of attitude has pleased Shulman because she no longer complains about marriage.
"There's a smile on [Adam's] face - mainly because I've been such a pain the past few months, going, 'Well, is marriage really a tool of oppression?' or, 'It was once just an exchange of property!' I have been utterly without romance regarding marriage for the past few months, so I think he's relieved that I'm kind of over it," she added.
Hathaway has previously admitted that she intended to stay single before she met Shulman.
Watch Anne Hathaway in the One Day featurette below: