The former Hibs, Doncaster and Kilmarnock midfielder signed a four-year-deal to become former boss Ally McCoist’s second signing of the summer in 2012 but has not been offered fresh terms.
The Northern Irishman was one of just two men to play in every season of Rangers’ journey through the lower leagues on their way back to the top-flight, ultimately helping to secure promotion to the Ladbrokes Premiership this season.
The 31-year-old played for the Ibrox side over 120 times and scored 32 goals.
He leaves the club having collected winners medals for the Third Division, League One, Championship and Petrofac Training Cup triumphs.
A spokesman for the club said: “Everyone at Rangers wishes Dean every success in his future career, and thanks him for their efforts during his time at the club.”
Shiels becomes the seventh man to depart Rangers so far this summer. Nicky Law, Nicky Clark and, David Templeton have all been released, while loan signings Dom Ball, Gedion Zelalem and Billy King have returned to their parent clubs.
Warburton has, however, made a start on his transfer business, with ex-England midfielder Joey Barton checking in alongside former Liverpool youngster Jordan Rossiter and Accrington Stanley pair Josh Windass and Matt Crooks.
And according to reports on Friday morning, the Englishman is also closing in on the signature of former Portsmouth, Tottenham and QPR midfielder Niko Kranjcar.