Sabres general manager Kevyn Adams originally hired Ellis at the Academy of Hockey.
"The traits that made Matt a successful NHL player are the same ones that have made him successful in player development in the years since," Adams said in a statement. "It's evident through his thorough planning and execution that Matt is passionate about developing young talent and our players will benefit from his approach to the game."
Ellis, a native of Welland, Ontario, also played for the Los Angeles Kings and Detroit Red Wings.
Throughout his career, Ellis played a leadership role in the Sabres developmental system, serving as captain of the Sabres AHL affiliate for three seasons in both Rochester and Portland.
Ellis also served as the head of coaching for the Buffalo Jr. Sabres beginning in April 2018. During his time with the organization, Ellis also coached several teams ranging from the 9U to 13U levels.