["British Journal of Management, EarlyView. ", "\nAbstract\nAs global commitment to the United Nations Sustainable Development Goals (SDGs) intensifies, firms are increasingly expected to contribute actively towards achieving these goals. Drawing from the relational view, this study investigates how firms’ alliance management capability enhances SDG performance, specifically through business model innovation and the moderating influence of strategic flexibility. A time‐lagged survey of senior managers from large Taiwanese firms (1114 managers from 311 manufacturing firms; 793 managers from 245 service firms) empirically tested a conditional indirect effects framework in which business model innovation mediates the relationship between alliance management capabilities and SDG performance, and strategic flexibility moderates both the direct and indirect paths. This study significantly extends the resource‐based view by demonstrating the crucial roles of business model innovation as a mediator and strategic flexibility as a moderator in translating alliance management capabilities into sustainability outcomes. Our findings underscore that strategically flexible firms are better positioned to leverage external resources from alliances for innovating business models that directly address SDGs 8 (quality employment) and 12 (resource efficiency). This research offers novel insights into integrated strategies for managing alliances effectively, emphasizing the importance of internal capabilities and strategic adaptability in enhancing firms’ contributions to global sustainable development.\n"]