Ageing of instrumentation and control (I&C) equipment at nuclear facilities has the potential to degrade mechanisms, which can in turn reduce safety margins and increase operating and maintenance costs. Obsolescence of I&C equipment can compound matters as suitable replacements become difficult to source. In 2019, the IAEA Technical Working Group on Nuclear Power Plant Instrumentation and Control acknowledged that relevant system and strategy guidance was required to implement modern technology at nuclear facilities. The purpose of this publication is to assist Member States in developing strategies to address ageing and obsolescence issues for I&C systems and it provides detail on modernization considerations and information from relevant recent operator experience. An appendix summarizes cable ageing management through condition monitoring, and several annexes describe Member States’ practices and experience with l&C ageing management and modernization.