The Dons announced Goodwin as their new manager on Saturday morning, less than a week after sacking Stephen Glass.
Goodwin, 40, leaves St Mirren after nearly three years in the job following his move to Paisley from Alloa in the summer of 2019.
St Mirren, who are fighting for a top-six place in the cinch Premiership and play Livingston away today, have commenced the hunt for a new manager immediately and Dons skipper Brown has been reported as one of the candidates for the job.
The 36-year-old joined Aberdeen last summer following an incredibly successful spell at Celtic. He signed a contract under then manager Glass to be a player/coach and took over the armband from Joe Lewis. However, it is unclear whether he will continue as part of Goodwin’s backroom team and does harbour ambitions of going into management.
Former St Mirren manager Jack Ross, who is free after leaving Hibs in November, is also one of the front-runners for the position.
In the immediate future, goalkeeping coach Jamie Langfield will take the Buddies team this afternoon in West Lothian alongside head of youth development Allan McManus and coaches Andy Webster and Michael McArdle.
A statement from St Mirren, who also have a Scottish Cup quarter-final against Hearts to look forward to, read: “St Mirren Football Club can confirm that Jim Goodwin has departed the club to join Aberdeen FC as their new manager.
“The board of directors and everyone at St Mirren would like to thank Jim for the role he has played at the club since taking over as manager in June 2019.
"We can also confirm that a deal is in place for assistant manager Lee Sharp to join Jim at Aberdeen.
“We thank Lee for his efforts in his time at St Mirren and wish him well for the future.
"Jamie Langfield will work alongside head of youth development Allan McManus, Andy Webster and Michael McArdle to take charge of first-team matters until a new manager is appointed.”