The versatile Morris signed for the club in May 2014 on a two-year deal from AFC Wimbledon.
He began his career at Cardiff City but managed just two professional appearances for the club prior to signing for Aldershot Town in 2010, which followed a short loan spell at Newport County.
The Welshman, often used as a central midfielder but capable of playing as a centre-back, right-back and a defensive midfielder, spent three years at the Shots before his final season was cut short due to cruciate ligament damage. Upon their relegation from the Football League, Morris was released by the club in May 2013.
On recovering from injury he joined AFC Wimbledon in January 2014 and appeared 17 times for the London club before electing to join the Gills the following summer.
Morris made his debut in the 2014/15 League One opener against MK Dons, and his well-taken goal against Yeovil Town in August 2014's Capital One Cup win remained the only time he had scored for the Gills prior to the 2016/17 season.
He signed a two-year contract extension with the club in June 2016