A country becomes a member of the IHO (81) by formally subscribing to the Convention of the IHO, administered by the Government of Monaco on behalf of the Organisation. Each IHO Member State pays an annual contribution, based on its fleet tonnage. This funds the IHO work programme, a secretariat and capacity building. The contribution is considerably less than for any other comparable intergovernmental organisation.

The IHO works together with inter-national organisations including the International Maritime Organization (IMO), the World Meteorological Organization (WMO), the Inter-governmental Oceanographic Commission (IOC), and the Inter-national Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) in the pursuit of its objectives:

- co-ordinating activities of national hydrographic offices

- ensuring uniformity in nautical charts and documents

- fostering adoption of reliable and efficient methods of carrying out and exploiting hydrographic surveys

- fostering development in the sciences of hydrography and the techniques employed in descriptive oceanography.

IHO decision making involves its Member States, usually represented by the national hydrographer or equivalent. Any Member State can make its voice heard when discussing and approving the Organisation's work programme, and benefits from proposed and agreed activities.

IHO Member States can take part in all aspects of the Organisation, including participation in committees developing and monitoring the Organisation's strategy, and in Working Groups tackling specific issues and developing and maintaining, for example, hydrographic and nautical cartography standards.

Member States wishing to establish or enhance their hydrographic capabilities benefit from collaboration in the 14 Regional Hydrographic Commissions and the IHO's capacity building programme. Member States also benefit from regional co-operation and access to assistance in fulfilling their international obligations under the International Convention for the Safety of Life at Sea (SOLAS), requiring that all coastal states:

... arrange for the collection and compilation of hydrographic data and the publication, dissemination and keeping up to date of all nautical information necessary for safe navigation.

This means that under international treaty law each Coastal State should ensure that hydrographic and nautical charting services are in place.

The UN General Assembly also adopted Resolution A/RES/58/240, in which it acknowledged the work of the IHO and its 14 Regional Hydrographic Commissions, and encouraged states to join the IHO by highlighting the IHO's capacity to provide technical assistance, facilitate training and identify potential funding sources for hydrographic services. Worldwide, however, only 80 of 151 states with coastlines are Members.

There are currently six states in various stages of joining the IHO; some of the remaining states are unaware of their hydrographic obligations or the benefits of giving national priority to hydrography and nautical charting. Part of the IHO's capacity building programme aims to raise awareness in States with little hydrographic capability, by high-level visits to ministers and identifying key hydrographic stakeholders and beneficiaries in each country.