According to IOC Resolution XXIII-12 membership in ICG/IOTWMS includes:
a) Member States of the IOC bordering the Indian Ocean.
Member States establish Tsunami National Contacts that represent the country in the coordination of international tsunami warning and mitigation activities.
27 Member States of the ICG/IOTWMS
b) Observers from other IOC Member States.
c) Invited Observers from other organizations (including NGO’s), programmes and projects in accordance with the IOC rules and procedures.