Instonians Cricket Club was founded in 1932 for past pupils and members of staff at the Royal Belfast Academical Institution. It continued as a separate organisation until the amalgamation of Instonians Rugby Football, Cricket and Athletic Clubs on 1st April 1962, the combined sections being known as 'Instonians'
On 31st May 1979 the title of the Club was changed to Instonians Rugby Football and Cricket Club, and on 1st April 1988 the Instonians Mens Hockey Club joined when the title reverted to ‘Instonians’.
On 27th May 1993 the original membership restriction was removed and the club went 'open'.
Instonians were based for many years at Shane Park, but this ground was sold to facilitate a move to Shaw's Bridge, where a ground-sharing arrangement with Cooke Collegians was set up, the move taking place in September 1999.