The pop star and her friends spent Saturday night at Caesars Palace in Las Vegas for the Canadian star's long-running residency.
Gomez, who arrived in a pink dress and heels and posed with a jumpsuit-clad Dion backstage, quickly shed her formal look in favor of a concert t-shirt.
Matching with her friends, Gomez, 23, documented the crew's exploits at the show through Snapchat.
"When you come to Vegas," she said, showing off her group's proud Dion fandom.
In other videos, Gomez sang along to Dion's hits, and even got a little emotional during 1996 track "Because You Loved Me."
VIDEO: Inside Celine Dion's Double Tragedy
Dion recently resumed her residency at The Colosseum following the death of husband René Angélil.
Her first, emotional show back last month was dedicated to Angélil and streamed online for 20 minutes.
"René is the only man that I have known all my life," she said during the February performance. "He always made me feel that we were on our first date, isn’t that amazing? Never talking bluntly, and always impressing himself in a soft and gentle way. We were one. And nothing has changed we will always be one."