| Country | Year Joined |
|---|---|
| Albania | 2009 |
| Belgium | 1949 |
| Bulgaria | 2004 |
| Canada | 1949 |
| Croatia | 2009 |
| Czechia | 1999 |
| Denmark | 1949 |
| Estonia | 2004 |
| Finland | 2023 |
| France | 1949 |
| Germany | 1955 |
| Greece | 1952 |
| Hungary | 1999 |
| Iceland | 1949 |
| Italy | 1949 |
| Latvia | 2004 |
| Lithuania | 2004 |
| Luxembourg | 1949 |
| Montenegro | 2017 |
| North Macedonia | 2020 |
| Norway | 1949 |
| Poland | 1999 |
| Portugal | 1949 |
| Romania | 2004 |
| Slovakia | 2004 |
| Slovenia | 2004 |
| Spain | 1982 |
| Sweden | 2024 |
| The Netherlands | 1949 |
| Türkiye | 1952 |
| United Kingdom | 1949 |
| United States | 1949 |