["Business Ethics, the Environment &Responsibility, EarlyView. ", "\nABSTRACT\nSustainability‐oriented leaders, guided by pro‐environmental values, play a critical role in advancing corporate sustainability goals. To refine our understanding of this relationship, we examine key boundary mechanisms shaping how sustainability leadership translates into environmental performance. We propose that stakeholder integration capability—grounded in firms' adaptive behaviours—provides distinctive advantages under conditions of business environmental uncertainty (BEU). Using survey data from 395 small and medium‐sized enterprises in Ghana, we find that sustainability leadership indirectly improves environmental performance through stakeholder integration, particularly under high BEU. These findings deepen understanding of how stakeholder participation enhances sustainability outcomes and highlight ways governments can foster firm–stakeholder collaboration through targeted policies and incentives.\n"]