Simpkins replaces Mike Brennan, who went 125-166 over 10 seasons and was let go earlier this week.
Simpkins brings deep ties to the area from his time as an assistant, a high school coach and a star player at Maryland.
"We are thrilled to welcome Duane Simpkins, a proven talent and respected coach into our AU Athletics family," said Billy Walker, director of athletics and recreation, in a statement. "His passion for positively shaping the lives of young student-athletes was evident during the selection process. His close ties to the area as a coach and player, along with a tremendous recruiting acumen and unbending character, make him an ideal choice to lead our program. Duane is truly a changemaker."
Simpkins spent the past eight years at George Mason and helped lure top talent to the men's basketball program under both Kim English and former coach Dave Paulsen. He served three seasons at UNC Greensboro prior to joining Mason, a stint that included roles as both assistant coach and recruiting coordinator.
He broke into college as Towson's coordinator of basketball operations under Pat Skerry.
Simpkins' local ties include stints as the head high school coach at St. Albans in Washington D.C. from 2007 to 2011. Prior to that, he was at Sidwell Friends School from 2005 to 2007.
Simpkins was a McDonald's All American at the fabled DeMatha Catholic High School under Hall of Fame coach Morgan Wootten. He later starred at Maryland, where he was a three-year starter and team captain under Gary Williams.
American went 17-15 overall this season, going 7-11 in the Patriot League. The Eagles have not reached the NCAA tournament since 2014, Brennan's first season.