The Lanark-born centre-back rose through the ranks at Celtic Park and went on to make 150 appearances for the Hoops, becoming club captain in 2007.
McManus joined Middlesbrough in 2010 and spent three years on their books, during which he also had two loan spells at Bristol City.
His last club as a player would turn out to be Motherwell, which he joined in 2013, and he will now begin a new chapter in his career as a coach with their academy.
"Obviously when it comes to the point where you are going to officially retire from playing, you always do so with a bit of a heavy heart," McManus told the official Well site.
"However, I've given this a lot of thought and I believe this is the right time for me, particularly with the club giving me this opportunity in a new era for academies in Scotland.
"I am also very excited to be learning from the great coaching staff we have at Motherwell at the moment; that was the main attraction for me. I want to develop as a coach and this is a wonderful opportunity."
McManus also won 26 caps for the Scotland national team between 2006 and 2010.