The former COO of Meta, 53, and her husband Tom Bernthal, 49, celebrated the holiday by getting into the groovy spirit of the 1960s with matching costumes.
The businesswoman and philanthropist's wore a dress covered in peace signs with a fringe vest and a pair of accessories that may have confused her phone: a pair of tinted sunglasses and a flower headband.
"You know it is a good costume when your phone ID doesn't recognize you," she jokingly captioned a series of snaps on social media. "Happy Halloween everyone!"
Sandberg and Bernthal, the founder and former CEO of Kelton Global, tied the knot in August.
The couple, who share a love of country music and got engaged on a ranch, got married at Trail Creek Ranch in Jackson, Wyoming.
"Tom and I met each other later in life — and that means we bring to this relationship a lifetime of friends we each had as well as some friends we've made together," Sandberg previously told PEOPLE.
RELATED VIDEO: Inside Sheryl Sandberg and Tom Bernthal's Wyoming Wedding: Serena Williams, Western Vibes and More
In an sweet personal touch, Rob Goldberg, the brother of Sandberg's late husband Dave, was their co-officiant — which the Option B author said was "as close to Dave's blessing" as possible.
Back in 2019, Rob first introduced Sandberg to Tom, his longtime friend — and the pair hit it off right away.
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
"In that first meeting we talked about death and divorce," he previously told PEOPLE. "We went pretty deep on that first date."
"I want people to see there's love after loss, love for us after death, love for us after divorce," she added.
At the wedding itself, their five kids — Sandberg has a son and a daughter, while Bernthal has three kids — all held important roles. In fact, Sandberg said their warmth and enthusiasm was the highlight of the night.
"Each of them gave a toast about our family — not just about their relationship with us, but about how close they are to each other," she said. "It was truly touching for both of us to see the five of them standing up there as siblings."