The 36-year-old, who signed a one-year deal with Shrewsbury in August, has now set his sights on management.
Morison enjoyed a 20-year career in the game that also included stints at Norwich, Leeds and Stevenage.
He scored 248 goals in 662 games and is believed to be the only player to score in each of England's top six divisions and at international level.
Morison has taken up a coaching role at Northampton Town where he first turned pro.
He said: "I've spent an amazing two decades as a professional footballer and have so many wonderful memories, but I feel the time is right to move on to the next stage of my career – and I couldn't be more excited.
“I learned so much while playing for my country and some great clubs, alongside and under so many fantastic players and managers, that I can't wait to put it all into practice as a manager and coach in my own right.
“Coaching at Northampton, the club I started at as an 18-year-old and continue to live nearby, is going back to where it all started for me as a player.
“As such it feels like a good place for me to start my coaching career and hopefully that can follow a similar path to the top as I experienced while playing. It was an offer I couldn't turn down."