Bride-to-be Katharine McPhee sizzles in yellow bikini

Katharine McPhee celebrated the holidays in an itsy-bitsy, teeny-weeny yellow bikini this year.

Taking to Instagram on Wednesday, the future Mrs. David Foster shared a sizzling snap of herself lounging in the Hawaiian sunshine.

“Mele kalikimaka is hawaii’s way… 💋🌼,” McPhee, 34, captioned on Instagram.

It didn’t take long for McPhee’s soon-to-be stepdaughter, Erin Foster, to playfully troll her in the comments.

“Grandma!!!! Wtf I don’t want to be next to you at the pool,” Erin, 36, wrote, to which McPhee replied, “Grandma carries it in the back. Don’t worry — you’ll see my cellulite when I stand up.”

McPhee confirmed her relationship with David, 69, in May, when they attended the annual Met Gala in May. The Grammy-winning producer proposed to the “American Idol” alum over the summer, while vacationing in Italy.

Though the couple has not yet announced a wedding date, both Erin and Sara Foster, 37, are happy to do what they can for the bride and groom.

“We’re down to help in any way we can,” Erin told Page Six back in September. “We love her.”