New couple alert?
A Twitter user captured video of the two dancing and singing along to the music, clearly having a great time together.
In the first video, the pair can be seen laughing during the performance of “I Want It That Way” as a few fans seem to crash their row.
In the second video, Steinfeld sings along, and Horan seems to spot the camera, but ignores it to sing along and enjoy the music.
And in the final video, they rock out to “Everybody.” And they weren’t the only celebs in attendance. Gwen Stefani can be briefly spotted sitting back and enjoying the concert.
The fun apparently continued after the concert. A source tells ET that after the Backstreet Boys show, the two spent time together at XS Nightclub in Wynn Las Vegas, where they sat together at a stage table with a few friends taking in a DJ set by Diplo and sipped on Absolut Elyx cocktails.
While the Pitch Perfect star and former One Directioner have yet to confirm or deny any relationship status, Horan did wish Steinfeld a happy birthday on Instagram back in December.
“Happy birthday to the loveliest person on the planet and one of my best friends @haileesteinfeld,” he wrote in the caption of the two cracking up at an award show.
For more on Steinfeld, watch the video below!