Mars penned this song with his Smeezingtons production team colleagues Philip Lawrence and Ari Levine. He told the story of the song to The Idolator: "That song came about just playing the chords, and I just freestyled "I think I wanna marry you!" and it felt good to say. It's that feeling when you're in Vegas, and you've had way too many drinks, and you love everybody, and you want to do something that you probably shouldn't do and you'll regret in the morning. We wanted to capture that feeling and put it in a song."

The song debuted on the Hot 100 for the first time after a version by the Glee Cast was performed on the "Furt" episode of Glee that aired in November 2010. The Glee version debuted at #32 whilst Mars's original rendition arrived at #91 the same week.

Explaining the "Dancing Juice" he mentions in this song, Mars told Rolling Stone: "I heard the term in London. I was telling some dude about a big night out, and he said, 'Yes, you were on that dancing juice.' It just resonated with me, so I stuck it into 'Marry You.' My manager just thinks the song is about him, though. He calls himself the Dancing Jew."