Zara, 30, quaffed champers as she joked around with rugby ace hubby Mike, 33.
He made her laugh by donning a beard, sunglasses and trilby hat "disguise" before holding up a "180" sign at the Alexandra Palace in North London.
The pair watched from the VIP area as Adrian Lewis, 26, beat Andy Hamilton, 44, to retain his PDC world darts crown, scoring eleven 180s.
Royle Family star Ralf Little, 31, held up a sign saying: "Mike Tindall is behind me!! Wow!"
David Williams, of event sponsor Ladbrokes, said: "Mark and Zara are big darts fans. The crowd held up signs asking how Prince Philip is."