ESPN's Adrian Wojnarowski first reported the news.
The Bulls promoted Boylen to head coach on Dec. 3 after firing Fred Hoiberg following a 5-19 start last season.
Boylen got off to an inauspicious start leading the team. Vincent Goodwill and Chris Haynes reported on December 10 that Bulls players went to the National Basketball Players Association to voice their concern with his "extreme tactics" during practice:
"After taking the helm from fired coach Fred Hoiberg on Monday, Boylen held three two-and-a-half-hour practices in his first week that included extra wind sprints and players doing military-style pushups. Calling for another lengthy practice after the back-to-back led to a near-mutiny and caused the players to reach out to the union, sources said."
The Athletic's Darnell Mayberry noted Chicago players were on the "brink of a full-blown mutiny."
Things seemed to eventually settle down as the season moved on. The Bulls are still in the early stages of their rebuild, so their 22-60 record isn't necessarily as important right now as the development of key young players.
Zach LaVine had the best offensive season of his career with 23.7 points and 4.5 assists per game. Lauri Markkanen averaged 18.7 points and 9.0 rebounds, though he has missed 44 games in his first two seasons due to injuries and an illness.
John Paxson, Bulls vice president of basketball operations, had high praise for Boylen in his end-of-season press conference with reporters:
"I've been sitting in on some player end-of-season meetings, and I can tell you that the thing that excites me about our direction with our head coach is his passion and his care level for our players and this organization. He wants to succeed, he wants our players to get better. He has a plan in place for all of them in order to do so this offseason, and that's very encouraging."
Boylen had never been a head coach in the NBA prior to taking over for the Bulls. The 53-year-old spent four seasons in that role at the University of Utah, going 69-60 with one NCAA tournament appearance from 2007-2011.
With nearly one full season of experience under his belt, Boylen has a much better understanding of what the job entails and how to maximize the talent on his roster. The Bulls have a solid nucleus in place and will add another high lottery pick this summer to build around.