The self-styled "Queen of Christmas" performed a rendition of her holiday hit All I Want for Christmas, in front of crowds gathered in the streets of New York City.
Scroll through the gallery below to see some of the best floats from Macy's Thanksgiving Day parade
Other celebrities including Kim Kardashian and Sir Paul McCartney also sent their best wishes to fans celebrating the American holiday.
In New York, Carey donned a bejewelled tiara and a flowing red dress, matching it with a red and gold umbrella — and was joined on stage by her twins Monroe and Moroccan, 11.
The Macy's parade, known for its spectacle, also featured a star-studded roster of performers, including Dionne Warwick, Gloria Estefan, Sean Paul, and Jimmy Fallon and the Roots.
"Happy Thanksgiving!" Carey captioned an Instagram post.
"Grateful and so proud of my beautiful kids Roc and Roe, grateful for the lambily and for the precious moments in life. Now it's reaaaallly time!!!"
Elsewhere, the Jonas Brothers took to the stage to perform at the halftime show of the Thanksgiving Day NFL game between the New York Giants and Dallas Cowboys.
Reality star Kardashian, 42, shared photos of a special Friendsgiving dinner with young incarcerated men at Camp Kilpatrick juvenile detention centre in Santa Monica, California.
She said she had spoken to the men about their "dreams and aspirations" and wished her fans a happy Thanksgiving.
Members of Kardashian's famous family also shared posts on Instagram sending their best wishes for the holiday.
High School Musical star Vanessa Hudgens said she had "so much to be grateful for" in her own online post, as she thanked her friends and partner, baseball star Cole Tucker.
"Happy day of giving thanks. Thru [tough] times I've always leaned on gratitude to lift my spirit," she wrote.
"So much to be grateful for. Mother Nature, Fam, friends, dis man [Tucker].
"The list goes on (and) on. I hope by focusing on the things your grateful for today your spirit is lifted."
UK celebrities also posted online, wishing their friends and colleagues across the pond a happy Thanksgiving.
Sir Paul shared a picture of himself with wife Nancy Shevell, writing: "Giving thanks for love - Paul #HappyThanksgiving."
Award-winning Ted Lasso star Hannah Waddingham shared a comical clip of herself from the panel show QI.
"Happy Thanksgiving my beautiful US pals. Much love and free turkey impression included," she wrote.