The Institute is a member of the European Physical Society, as well as the European Microscopy Society, European Optical Society, and the International Commission for Optics. It has an active involvement in The International Union of Pure and Applied Physics, to which it is the adhering body for the UK and Ireland. IOP also adheres to the International Union of Radio Science (URSI) and International Union of Theoretical and Applied Mechanics (IUTAM).

The aim is not just to represent British and Irish physicists through these organisations, but also to help the international organisations to work effectively for the benefit of physics and physicists worldwide.