Adams replaces Marianne Stanley, who resigned last month.
Adams was a point guard who played 12 years in the NBA and was an assistant coach for two years with the Memphis Grizzlies. Adams also coached the Richmond Rhythm of the International Basketball League.
"I am excited for this tremendous opportunity," Adams said after the announcment was made Tuesday. "I have always been a fan of the Mystics. I am ready to go to work."
The Mystics have had seven coaches in their seven years in the WNBA.