A rapid implementation of potentially more sustainable sector structures in newly industrializing countries (NICs) is of key importance to reach global sustainability. The conceptual basis for assessing such “leapfrogging” potentials is however still rather weakly developed. The present paper elaborates an encompassing conceptual framework drawing on the technological innovation systems literature and adding an explicit geographical focus that embeds an NIC's innovation system in its international context. From this, we derive six ideal-type leapfrogging trajectories. The framework is applied to the case of a potential transition to onsite wastewater treatment in China. Empirical evidence is based on 30 expert interviews with representatives from companies, universities, authorities and associations in China and Europe. Our results suggest that leapfrogging in the Chinese wastewater sector might develop in either an integrated “international innovation system” trajectory, where Chinese and international actors closely interact, or in an “international competition” trajectory, where Chinese actors endogenously build up technological leadership in strong competition to international actors. We conclude by outlining policy implications and by discussing future research priorities for leapfrogging and transition studies. Display omitted ► This study aims at conceptualizing leapfrogging in newly industrializing countries. ► We develop a frame for analyzing leapfrogging with spatially coupled technological innovation systems. ► The frame is applied to onsite wastewater technology in China. ► Leapfrogging could be conceivable in China either in an international cooperation or competition trajectory. ► Implications for policy making, leapfrogging and transition studies are discussed.