Deen is a left back who can also play in the heart of midfield. He is also a Sierra Leone international player. Deen made his senior debut for Sierra Leone on 24 March 2007 against Togo in a 2008 African Nations Cup qualifier played in Freetown.

Ahmed Deen arrived at the Moss Rose in the summer of 2008 from fellow League one club Peterborough United. He was once on the books as a trainee at Leicester City.

He enjoyed spells with a variety of non-League teams, including Bishop's Stortford in the Conference South. He was released by Macclesfield Town at the end of the 2008–09 season, and signed with Barnet in August on a short-term deal. After some impressive performances he signed a two-year deal in September, linking up with his cousin Albert Jarrett.

He scored his first goal, a free-kick, for Barnet in a 3–1 away win against Northampton Town on 4 September 2009. Deen was due to sign for Dover Athletic on loan in March 2010 but this deal was called off as the Bees already had Daniel Leach and Joe Tabiri on loan at Dover, and a third would have breached league rules. Deen was released by Barnet at the end of the 2009–10 season.

Deen joined Hayes & Yeading United in August 2010, teaming up once again with former Barnet goalkeeper Lee Harrison, making his Conference debut in the home win over Bath City. He was released by Hayes & Yeading United in February 2011. In the same month, he joined Dulwich Hamlet.

In October 2011, Deen signed for Southern League club Cambridge City.

In December 2011, Deen signed for Conference South club Thurrock. He re-joined Dulwich Hamlet in August 2012, and was a regular choice at left-back as the Hamlet won the Ryman League Division One South. Continued solid performances in the Hamlet's return season to the Ryman Premier Division earned him a place in the Non-League Paper Team of the Season for 2013-14.

During the 2014-15 pre-season, it was announced that Deen would be leaving the Dulwich Hamlet playing staff, although he would be retaining links to the club through his work with the Dulwich Hamlet Football in the Community Programme.

Michael Deen's new chapter in his life is now with Aveley Football Club ahead of tonight's game at home to Harlow Town.

Justin Gardner said "It's great that we are able to bring him to the club, he's vastly experienced and that's something that could be added to help some of the younger players"

Everyone at he football club would like to welcome Deen to the club and wish him the best throughout his time here.