Young guns Robert Stannard and Callum Scotson, along with Alex Edmondson, Damien Howson and Nick Schultz, have also signed on.
Mitchelton-Scott's 2021 squad will now feature 11 Australian riders in total, with Kaden Groves, Lucas Hamilton, Michael Hepburn and Michael Matthews already on board.
Inaugural member Durbridge will now enter his 10th year with the team and Head Sport Director Matt White was delighted to secure his services.
"We know what we get with Durbo," White said.
"He has been here since the start, he certainly hasn’t finished developing, he is a go-to guy for us across 10 months of the season so it’s great to have him commit to a couple more years with the team.
“This year was a different year, we had an agreement with him that he would miss this year’s Tour to concentrate on the world championships time trial and the Classics, but Durbo is always a guy I would want to take to the Tour de France.
“With his versatility you can take him to a lot of races on the calendar, and he is always committed to whatever plan we have.
"He has his specialities, which we want to keep developing, but he is also a very loyal teammate and to win Grand Tours and big stage races you need guys like that in your roster."
The 2021 season will start in February.