The 22-year-old – who is also the U23 Italian road and time trial champion – joins from the Dutch SEG Racing Academy, where he's spent the past two seasons.
"It's really amazing to be given the opportunity to turn professional with one of the best teams in the world like Mitchelton-Scott," said Affini on the team's website. "It is definitely a dream come true for me.
"I'm excited to see what the future will bring, and I think that here I have a great chance to start a new chapter and continue to expand on the development started two years ago with SEG Racing Academy. I can't wait to get started."
This season, Affini also won the prologue time trial at the U23 Giro d'Italia in June, and went on to take the individual time trial title at the Mediterranean Games later that month.
While happy to take advantage of the Italian's time trialling abilities, Mitchelton-Scott are also keen to introduce Affini to their Classics squad.
"Edoardo is one of the most exciting prospects to come out of Italy in recent years," said head sports director Matt White. "He is a super strong time trial talent and a rider that we'll be looking to integrate into our Classics group, and develop his potential over the next few years.
"His results this year speak for themselves, and it was an important factor for Edoardo to go a team where he is able to continue his time trial development and progression on the same upward curve.
"Since our inception, we have achieved results and created a strong pedigree in that pursuit, and I am sure Edoardo will be a great fit," White said. "We have a great track record at developing young talent, and within the team we have a genuine care for the riders and place great importance on allowing them to progress naturally without any undue pressure and that won't be any different for Edoardo."