Hopkins will sign a six-year deal with Washington, according to ESPN's Jeff Goodman.
"I'm extremely excited to welcome Mike and his family to Seattle," Washington athletic director Jennifer Cohen said in a statement. "His résumé and reputation within the basketball community made him stand out to us, but ultimately it was his vision for Washington, his passion for teaching and developing student-athletes and his close alignment with the core values of our institution and department that made it more than clear that he was the right fit for us."
Hopkins, 47, has worked under Jim Boeheim at Syracuse since 1996, and he also played college ball for the Orange. He was expected to be the successor to Boeheim when the veteran head coach retires, having been named the coach-in-waiting in 2015.
"He wants to build a legacy, felt like the opportunity was special at Washington, and also wanted to make sure he did right by his mentor and father figure, Jim Boeheim," a source close to the situation told Goodman.
Later Sunday, Boeheim signed an extension with Syracuse that will run beyond the 2017-18 season. The school indicated that the contract was in response to Hopkins taking the job at Washington.
"Mike accepting the position at Washington has put us in a unique position," Syracuse athletic director John Wildhack said in a statement released by the school. "The circumstances are different now than they were when he was named head-coach-in-waiting."
Hopkins, a California native, went 4-5 as interim head coach in 2015-16 while Boeheim was suspended. He has been mentioned in searches for other head-coaching jobs previously, including as a finalist for Oregon State's top job in 2014.
"I can't express enough thanks to Coach Boeheim for so many years of mentorship and guidance," Hopkins said. "The timing is right for me and my family to make this move."
Hopkins replaces Lorenzo Romar, who was fired earlier in the week after 15 seasons with the Huskies.