This study examines climate justice within the broader framework of sustainable justice to reassess the relationship between power and legitimacy in North–South climate governance. As climate change intensifies, inequalities between countries that contribute most to greenhouse gas emissions and those that suffer the greatest impacts raise fundamental questions of fairness, responsibility, and authority in global governance. While climate justice is widely discussed, it is often treated separately from wider justice frameworks and from structural power dynamics in international relations. This paper addresses that gap by integrating climate justice into a sustainable justice perspective and linking both to the power legitimacy dialectic. Using a qualitative, normative–analytical design based on document analysis of major climate agreements, scientific assessments, and climate finance reports from the post-2015 period, the study evaluates governance arrangements through four justice dimensions: distributive, procedural, recognition, and intergenerational justice. The findings reveal persistent justice deficits in burden-sharing, participation, vulnerability recognition, and long-term responsibility, which contribute to legitimacy concerns in the climate regime. The study proposes a power legitimacy analytical model connecting structural resources, norms, and institutions. It argues that aligning climate governance with justice principles can strengthen credibility, trust, and cooperation, making justice a practical foundation for more stable and effective global climate governance.