The Girls star, 26, posted a photo on Instagram of her rumored beau's band Wednesday night, writing: "Truly Glorious."
The We Are Young group played at the Grammy nominations concert that aired on CBS in addition to picking up a few noms of their own.
"They're trying to keep it a secret," a source told Us magazine this past September, adding that Dunham's love-life in the past has consisted of "multiple gay ex-boyfriends."
Related: Grammy Nominees Announced
The two have already collaborated on projects including a video for The New Yorker's iPad application and a soundtrack-in-the-works for Dunham's HBO show.
Related: Girls Season Two Trailer
Another clue is that Dunham wore a dress made by Antonoff's sister for her appearance on The Colbert Report on May 3.
What do you think? Is this a good match for the funny girl? »
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