The current Australian road race champion, who won his title at the start of this season, will continue with the WorldTour team until at least the end of 2020.
The 24-year-old has been with the team since the start of 2016, and feels he's in the best place to continue to improve.
"I’m stoked to sign with the team for another two years. It's an amazing group of guys – not only the riders, but the staff as well, which makes racing my bike so enjoyable," Edmondson said in a team press release.
"I feel as though Mitchelton-Scott is a great fit for me as there’s a huge variety of guys in the team that I have the opportunity to learn from, plus race alongside."
Edmondson comes from a track background, and is a two-time team pursuit world champion, and won the individual pursuit title in 2014, as well as the silver medal in the team pursuit at the Rio Olympics in 2016.
He also raced extensively on the road with the national team at under-23 level, both in Australia and in Europe, before turning pro, winning the 2015 U23 Tour of Flanders ahead of Gianni Moscon, who now rides for Team Sky.
The Classics, Edmondson said, is where he sees his future: "For me over the next two years, I'm looking to keep developing and, of course, try to give the Classics a really good shot because that’s always been a big dream of mine."
Head sports director at Mitchelton-Scott, Matt White, is thrilled to have retained Edmondson's services for the next two seasons.
“Alex is continuing to make the transition from a world-class track rider to a full-time road rider. We see a real future with Alex, especially in our Classics group, and exposure to high-level racing will be key to his development, and this year's Vuelta a España was a crucial step for his development for the spring of 2019," said White.
"We see him growing into a real Classics specialist, and that takes time. We are excited to be able to continue his development with us."