The party, held at the Berghaus Eggli restaurant in Gstaad, was a true reflection of Andrea and Tatiana's fun, relaxed approach to life.
Click on photos below for a gallery of pre-wedding celebrations.
Tatiana and friends days before her wedding
Guests were spotted arriving by cable car, wrapped up in red blankets and enjoying the fresh mountain air. Music played as those invited mingled on the outdoor terrace and warmed up with steaming, hot drinks served out of bright, red mugs. Candles in lanterns were dotted around the alpine venue, adding a touch of romance and magic to the ambiance.
It certainly looked like the guests were enjoying themselves as they flooded their Instagram and Twitter feeds with enviable photos. Much like in the style of Andrea and Tatiana's summer wedding celebrations, guests donned glamorous outfits with a dash of novelty fun.
Fashion heiress and close friend of Tatiana, Margherita Missoni, looked on-trend as ever in a blush pink, fur-lined coat with matching fur boots, while editor Fabiola Beracasa showed off her white fur jacket, glamorous, coiffed hair and diamond earrings in a selfie.
Andrea's younger brother Pierre Casiraghi opted for a more eccentric look, sporting red and white leg warmers, a matching red bobble hat and flip-up glasses. Other notable faces in the crowd included Monegasque royals Prince Albert and Princess Caroline, and dress-maker Valentino, who designed Tatiana's show-stopping wedding gown.
Margherita Missoni poses in a green wig
The celebrations started earlier for some of the wedding guests, who flew out to Gstaad a couple of days before the weekend nuptials. Tatiana spent quality time with Margherita and the fashionista's newborn son Otto, and later enjoyed a girls' night out with her close friends including Olympia Scarry. Margherita looked to be having a great time, donning a colourful wig and posing with friends for photos.
During the day, guests made the most of the perfect skiing weather, hitting the slopes and taking stunning snapshots from mountain tops.