The Wales international has decided to leave Pittodrie in an attempt to get his career back on track.
Brown, who moved to Aberdeen from Blackburn in July 2011, made 28 appearances during his time in Scotland.
"Jason made it clear to us he was keen to return to England and continue his career," Fraser said.
"He is a proud member of the Welsh international team and in order to maintain his place in the squad he feels it is vital for him to be playing every week.
"The club wish Jason all the best with his future career."