Williamson is the third Duke player in five years, following Jahlil Okafor and Marvin Bagley III, to win both individual honors in the same season. Before those players, the double had never happened in the history of the conference.
The 18-year-old Williamson received 49 of 70 votes for Player of the Year and 47 votes for the rookie honor. Blue Devils teammate RJ Barrett finished as the runner-up on both ballots.
Williamson, the projected No. 1 pick in the 2019 NBA draft, has averaged 21.6 points, 8.8 rebounds, 2.2 steals and 1.8 blocks per contest across 26 games with Duke this season.
His total scoring output still ranks second in the conference despite him sitting out of action since suffering a knee injury against North Carolina on Feb. 20. Blue Devils head coach Mike Krzyzewski said Saturday that Williamson is expected to return in the upcoming ACC tournament.