Effective environmental governance is deemed essential in advancing the Sustainable Development Goals. However, environmental dimensions have no specific reference across the SDG 16 targets and indicators. In achieving SDG 16—the realization of peace, justice, and strong institution, polycentric environmental governance involving multiple actors across scales deserves thoughtful consideration. This study illustrates the potential of a polycentric approach to environmental governance in achieving SDG 16, using case studies of forest, watershed, and transboundary bushland and seascape management in Southeast Asia and Eastern Africa, namely Vietnam, Indonesia, and the Kenya–Somalia cross-border. By highlighting four key elements of polycentric governance namely, political will, legal framework, support from higher-level governance and capacity building, the case studies demonstrate that polycentric governance play a significant role in achieving three environment-relevant SDG 16 targets, yet these targets are silent about environmental governance dimensions. Since many conflicts arise from the environment and natural resources sector, we suggest that (i) polycentric environmental governance be strongly pursued to achieve SDG 16, and (ii) SDG 16 includes indicators specifically directed on polycentric environment and natural resource governance.