The 45-year-old singer and 35-year-old actor came together for their 4-year-old twins, daughter Monroe and son Morrocan. Carey dressed as a witch, while Cannon, Monroe and Morrocan went as the Hulk, Batgirl and Batman, respectively.
"A #ghoulicious time with dem babies #halloween," the singer wrote on Instagram.
"Family Festivities! #Ncredible Hulk Halloween!" Cannon added.
Carey hosted a family-friendly celebration at a rented Beverly Hills mansion, where she partied with boyfriend James Packer later in the evening.
The fete featured a dance floor, candy apple martinis and plenty of Sugar Factory candy.
"Mariah and Nick got along great and were super friendly towards one another," a source told E! News of the estranged couple.
An insider told TMZ Cannon left before Packer showed up at the party.
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