In the Instagram Reel, Grimes, her husband, 35-year-old Josh Beech, and their two children, four-year-old Bowie and one-year-old Kingsley, transitioned between their normal outfits and their costumes.
Throughout the clip, the family snapped along to a version of Vic Mizzy's song, "The Addams Family."
Grimes stunned wearing a jet black wig and a long-sleeve gown as she dressed as Morticia Addams.
Beech rocked a black and white pinstripe suit and a pencil-thin moustache to play Gomez Addams.
Bowie wore a black wig with braided pigtails and a black dress as Wednesday Addams, and Kingsley dressed in a black and white striped T-shirt to play a younger Pugsley Addams.
"Now this is our kind of family tradition," Grimes captioned the video along with a black heart emoji.
The "90210" and "Degrassi: The Next Generation" actress shared several photos in a separate post, where the family showed off their "amazing" costumes.
"The kids faces in the first pic," the Toronto-native star joked in the caption. "One hundred per cent in character! Last pic is the real gem though. Couldn't imagine a better way to spend my birthday than dancing at a monster mash (at the zoo) with my favourite ghouls!"
Fans were quick to show their love for the family and their costumes in the comments section of both posts.
"This is so creative and awesome! you guys look wicked," a fan added.
"So on brand for you guys," another chimed in.
"I love this! Y'all are iconic!" someone raved.
"I feel like you're giving goth Celine Dion, and I love it!" someone else commented.
"Last pic is incredible, especially with the filter!" penned a follower.
"Recast 'The Addams Family' with the Beech family," one person suggested.