The 48-year-old singer has officially returned to Sin City for her new residency, The Butterfly Returns, kicking off opening night on Thursday with a brand new, butterfly-themed set and plenty of glitzy costumes at The Colosseum at Caesars Palace.
"What's up, Las Vegas?" Carey, clad in a body-hugging silver fringe dress, strappy platform heels and sparkly chandelier earrings, exclaimed as she opened the show. "How you feeling, honey? Hello, darlings."
The blonde beauty then changed into a stunning black gown with sheer overlay, showing minor PDA onstage with her boyfriend, backup dancer Bryan Tanaka, as she sang "Fantasy."
Midway through the show, Carey announced that she'd be bringing some "very special guests" to the stage -- her 7-year-old twins, Monroe and Moroccan, whom she shares with her ex-husband, Nick Cannon.
As she belted out her classic 1995 hit, "Always Be My Baby," Roc and Monroe adorably held onto their own mics and waved to the audience.
"I'm not sure what we're doing but they're having fun," Carey explained.
While all her outfits were incredibly fab, Carey rocked one of her best looks of the night towards the end of the show -- a sparkly, white-and-silver gown adorned with a feather train.
"These dresses, they're long," she joked. "You never know what you’re gonna step on."
She closed out opening night with a beautiful rendition of "Hero," telling the audience, "I guess it's one last song, a fan favorite."
"I wrote this song a long time ago," she quipped. "'Til next time, dahlings. Love you much."
The mother of two appears to be more confident than ever following her recent weight loss. A source told ET last month that she's actually the happiest she's ever been!
"She seems to be exuding happiness and she is," the source said at the time. "She has had big changes in her life for the better. Both dropping her manager, Stella [Bulochnikov], and coming clean about her struggles with bipolar disorder have been a huge relief and it shows."