This study comparatively analyzes China–United States space competition and its implications for international security. It asks: “What dimensions does this competition have, and how does it affect international security?” The hypothesis holds that shifting technological capabilities and expanding military and counterspace capacities redefine the balance of power and increase security complexities. The study uses descriptive-analytical and comparative methods, informed by power cycle theory and the modern geopolitical approach. Findings across three analytical levels indicate: (1) The United States retains technological and infrastructural superiority; however, China seeks to improve its position and narrow the space-power gap through independent navigation systems, technological investment, and exploration; (2) Counterspace capabilities and military reliance on satellite infrastructure have made space important to deterrence calculations and mutual vulnerability; (3) Intensified competition affects international stability by increasing strategic uncertainty, complicating deterrence, and heightening militarization risks. The results show that China–United States space competition forms part of the redefinition of international power hierarchies within the evolving global power order. Technological superiority and infrastructural autonomy have become fundamental components of strategic power. Therefore, space security depends not only on balancing major powers’ capabilities but also on multilateral confidence-building, strategic transparency, crisis management, and rules for responsible conduct.