The severe global hazards posed by marine microplastics must be given attention. This study evaluated the current international legal framework, and offers forward-looking recommendations for enhancing international law. The analysis began by examining the unique characteristics and profound impacts of marine microplastics, underscoring the necessity of a corresponding international regulatory regime. Through a thorough review of the existing global and regional legal instruments—both soft and hard laws—we identified key issues and challenges in the international legal response to marine microplastics, particularly in terms of legislation and enforcement mechanisms. The study emphasizes the urgent need for strengthened international legislation, including the potential development of a specialized international treaty, and calls for the enhancement of compliance mechanisms to effectively combat marine microplastic pollution and support the broader goal of sustainable development.