As the Global South gains increasing prominence in international politics, the South Atlantic has re-emerged as a strategic geopolitical space amid intensifying competition between China and the United States, the evolving backdrop of several global tensions, and the ongoing interest in the region’s vast natural resources. While traditionally perceived as a secondary theatre in global geopolitics, the South Atlantic has drawn renewed attention from extra-regional actors, not only due to security concerns but also because of its economic and socio-environmental relevance. For Brazil, the South Atlantic is of paramount importance. A significant share of its population resides along the coast, and nearly all of its international trade depends on Atlantic maritime routes. Concurrently, China has expanded its presence in the region, offering both opportunities and challenges to Brazil’s foreign policy. This dynamic unfolds within a broader context that includes South–South cooperation, Sino-American competition, regional security arrangements such as Zopacas, and Brazil’s engagement with neighbouring nations, the Lusophone world, particularly in Africa, and the BRICS. As a result, the interplay between Brazil’s diplomacy and maritime strategy, China’s economic outreach, and new geopolitical considerations shapes the South American country’s position in regional governance and global affairs. This chapter investigates the main implications of China’s growing economic presence in the South Atlantic for Brazil’s geopolitical strategy. While studies on Brazilian foreign policy in the South Atlantic remain underdeveloped, the impact of China’s initiatives on these strategies is even less explored, particularly within the context of the balancing that Brazil has to promote to accommodate its diverse relations and interests. By filling this gap, this chapter aims to contribute to the literature by examining key aspects such as economic and security cooperation, maritime governance, and regional institutional frameworks. Methodologically, the study employs a qualitative approach, drawing from academic literature, government documents, and other relevant data. The findings are expected to provide new insights into the evolving dynamics of the South Atlantic and Brazil’s efforts in maintaining its strategic autonomy amid growing geopolitical challenges.