The development of diplomatic relations between major countries continues to experience significant dynamics. In recent years, we have witnessed an increase in multilateral cooperation, as well as tensions due to increasingly complex geopolitics. This article will discuss key issues in diplomatic relations between major countries. One striking development is the increasing economic and trade cooperation between countries such as the United States, China and the European Union. For example, China’s Belt and Road Initiative Plan focuses not only on infrastructure development, but also on deeper economic integration with various countries, including developing countries. This prompted a response from Western countries seeking to strengthen their position through fairer and more transparent trade agreements. In addition, climate diplomacy is in the spotlight, especially after the COP26 conference held in Glasgow. Major countries, including the US and China, are committed to increasing greenhouse gas emission reduction targets. However, challenges remain, such as differences in approaches and national interests that often clash. The Paris Agreement remains the foundation for these countries to achieve positive results in climate cooperation. Tensions also arise from the situation in the Asia-Pacific region, particularly related to China’s military activities in the South China Sea. The United States and its allies, such as Japan and Australia, strengthen alliances through joint military exercises and security agreements. These measures aim to respond to China’s military expansion while ensuring freedom of navigation in international waters. In the Russian context, relations between Russia and Western countries, especially after the invasion of Ukraine, have deteriorated drastically. Economic sanctions imposed by Western countries have had a major impact on the Russian economy. Nevertheless, Russia continues to strengthen ties with countries such as China and India, creating new blocs that are likely to challenge the more traditional international order. Technological developments also play an important role in contemporary diplomatic relations. Large countries compete in technological innovation, especially in the fields of artificial intelligence and cybersecurity. Uncertainty regarding data ownership and user privacy is also a major theme in diplomatic discussions. Cooperation in the field of technology is now considered as important as economic and security cooperation. At the same time, multilateralism has again been raised as a solution to many global issues, including health and security. Organizations such as the UN and WHO are trying to bring together major countries to face global challenges such as pandemics and climate change. Although cooperation is often hampered by conflicting national interests, efforts to return to the negotiating table remain an important step in diplomatic relations. By witnessing these developments, the world is seeing how major countries are adapting to new challenges, while trying to find common ground in international cooperation. Negotiating mutually beneficial agreements is becoming increasingly complex, but remains crucial for future global stability.