Robertson's renewal is for a further three years, tying him down to the ARU and Super Rugby's the Waratahs until 2020.
The 23-year-old, who made his debut for the Wallabies against South Africa last year and has since amassed 15 Tests, said: "New South Wales is home for me. I'm very passionate about the Waratahs and Wallaby jersey and it means so much to me to get the chance to pull them both on.
"There's plenty still to do this season with the Wallabies, but I'm also really excited about next year with the Waratahs.