In the 21st century, China’s rise has been shifting global and regional geopolitical scenarios. Faced with its growth and fears of being perceived as a threat, China sought to associate its economic and political emergence with the preservation of the current international system, emphasizing speeches about a peaceful development and harmonious world in which it would be an actor who wants to grow and accommodate the world order. However, changes in the balance of power and its continued rise have caused China’s behaviour to change in its own region, especially regarding maritime disputes and affecting other countries’ perceptions. By applying Neoclassical Realism, this paper analyses the Chinese foreign policy in the 21st century, elucidating its behaviour in terms of the country’s action and reactions regarding the dispute over the Senkaku/Diaoyu Islands and shows the perceptions of other countries to that behaviour. The article concludes that perceptions concerning the balance of power, Chinese capabilities, nationalism, regime legitimacy, and on leadership images affect the intensity of Beijing’s responses and foreign policy about maritime territorial disputes. Also, the article shows that China’s growing assertiveness in both the East China Sea and the South China Sea is pushing countries that have territorial disputes with China to grow closer.