It ends a one-season stint with Belgian team Quick-Step Floors for 32-year-old Bauer, who contested this year's Tour de France and helped set up German sprinter Marcel Kittel for five stage wins.
Orica-SCOTT sporting director Matt White said Bauer was a rider they had targeted for some time.
White said the looming reduction in team rosters made versatile riders such as the big Kiwi valuable.
Bauer said he was delighted with the move.
"As an Australian team, for me it's the closest thing to riding for an outfit from back home," Bauer said.
"I know all the boys on the team really well, and have done for quite some years, so it seems like the perfect fit.
"I have proven myself as a reliable and strong workhorse over the years and a big goal for the season will be to line up alongside Luke Durbridge and Matteo Trentin in the Northern Classics and ride for the win."
Storer and Hindley head to Sunweb from Mitchelton-Scott
Young Australians Michael Storer (20) and Jai Hindley (21) have made the jump to the WorldTour and Team Sunweb, joining Michael Matthews and Chris Hamilton, on the German registered outfits roster.
Storer signed on for a two-year stint while Hindley inked a three-year deal.
“I’m super excited to be joining team Sunweb for 2018," Hindley said. "I think the team have shown they are quite big on innovation as well as developing young guys and this really stood out for me when looking for a new team.
"For 2018 my main goals would be to try to grow as a cyclist whilst learning as much as I can, and to try to adapt to the professional style of racing.”
Storer finished fifth overall at the Herald Sun Tour, third at the Giro Ciclisto della Mont Blanc, took a stage win at AnPost Rás in Ireland and 15th overall at the Santos Tour Down Under.
I’m looking forward to working with the team, the riders and staff and also the new challenge that will come with racing in the WorldTour," Storer said.
"When considering teams, the development pathway was really important for me because I’m still only riding my second year as an U23. I wanted a team that provides the best support for me to become a better rider and somewhere I could become athlete on and off the bike."