It was the first individual final since Monterrey in April last year for the 29-year-old left-hander, who won the Australian and U.S. Open titles in 2016.
Angelique Kerber made the ideal start to 2018, winning the Sydney International after beating Ashleigh Barty in the final on Saturday.
Barty, who'd been looking to become the first Australian woman to win in Sydney since Alicia Molik in 2005, could convert only one of seven break points, while racking up 38 unforced errors to Kerber's 13.
In a momentum-boosting buildup to the Australian Open, which starts Monday, Kerber had wins over Lucie Safarova, No. 2-seeded Venus Williams, former Australian Open finalist Dominika Cibulkova and Camila Giorgi before beating Barty to claim her 11th career title.
"I am playing wonderful tennis again and I am just feeling great".
WTA SYDNEY - Giorgi beats Radwanska to meet Kerber
Defending champion Gilles Muller was knocked out of the Sydney International men's event by unseeded Frenchman Benoit Paire 6-4, 6-4.
"I am playing awesome tennis again and I am just feeling great", said the 2016 Australian Open and US Open victor.
The 21-year-old Barty needed one hour, 58 minutes to see off the challenge of Russian-born Gavrilova as both players struggled to hold serve throughout the match. The 2016 Australian Open champion and former No. 1-ranked Kerber won four singles matches at the Hopman Cup, helping Germany reach the final against Switzerland, and followed up with five wins in Sydney.
In the end, Kerber's on-court composure was what counted against her younger counterpart, earning three championship points and claiming the silverware at the first opportunity.
"It's been a pleasure playing here this week".
In the build-up to next week's Australian Open, Spaniard Bautista Agut defeated Argentine Juan Martin del Potro 6-1 4-6 7-5 to win the tournament in New Zealand for a second time.