The 18-year-old was selected with pick No. 11 in the 2014 National Draft and played 12 games this season.
“I couldn’t have asked for more in my first year, getting a look at a Grand Final,” Duggan told the Eagles’ website.
“The only way it could have been better would have been to win the Grand Final and that has to be our aim. I really want to be a part of it.”
“It’s exciting to have extended my contract already, to get it done now so I can just concentrate on getting right for next year.”