Simmons beat out Utah Jazz guard Donovan Mitchell and Boston Celtics forward Jayson Tatum. The award was presented at Monday night's NBA Awards show in Santa Monica, Calif.
"I'd like to thank my family, to start off with," Simmons said. "My family, friends, you know I wouldn't be here without them, and my teammates of course and my great coach (Brett Brown), and the city of Philadelphia for really embracing me."
Simmons was taken with the top pick in the 2016 NBA Draft, but a broken foot sidelined him for the 2016-17 season.
The 6-foot-10 guard averaged 15.8 points, 8.2 assists, 8.1 rebounds and 1.7 steals over 81 games last season.
Simmons, who turns 22 next month, helped the 76ers advance to the Eastern Conference semifinals, where they lost to the Boston Celtics in a five-game series. He averaged 16.3 points, 9.4 boards, 7.7 assists and 1.7 steals in the playoffs.
Pacers guard Victor Oladipo is the NBA's Most Improved Player after a stellar first season in Indiana that ended in a playoff showdown with LeBron James and the Cleveland Cavaliers.
He beat out fellow finalists Clint Capela of the Houston Rockets and Spencer Dinwiddie of the Brooklyn Nets.
"Shout out to the Pacers organization for believing in me," said Oladipo, who was dealt to Indiana last offseason in the deal that sent Paul George to the Oklahoma City Thunder. "It's only the beginning for us."
Oladipo, 26, averaged a career-high 23.1 points with 5.2 rebounds, 4.3 assists and 2.4 steals to earn his first career All-Star selection, as well as a spot on the All-NBA third team and the All-Defensive first team.
In the playoffs, Oladipo averaged 22.7 points, 8.3 boards, 6.0 assists and 2.4 steals, but it wasn't enough to send the Pacers onto the conference semi-finals, as they lost to the Cavaliers in seven games.
Utah Jazz center Rudy Gobert won the NBA's Defensive Player of the Year award, beating out Anthony Davis of the New Orleans Pelicans and Joel Embiid of the Philadelphia 76ers.
Gobert, who turns 26 on Tuesday, missed 26 games during the regular season with multiple injuries, but still anchored a Jazz defense that posted the second-best defensive rating (101.6) in the NBA last season.
The Frenchman averaged 13.5 points, 10.7 rebounds and 2.3 blocks in 56 games to earn his second straight NBA All-Defensive first-team selection. Gobert led the league in blocks in 2016-17 with 2.6 per game.