This study focuses on the boundary-spanning nature of sustainable business model innovation, studying multi-stakeholder engagement and alignment. Drawing on the concept of boundary work, we explore the different types of organizational boundary changes between focal companies and their external stakeholders, investigating specifically the process of exploring, negotiating, disrupting and realigning organizational boundaries. Based on an exploratory study of nine different sustainable business model initiatives from for-profit and non-profit organizations, our analysis shows how actors involved need to find alignment at normative, instrumental and strategic dimensions in order to achieve sustainable value creation. However, complexity for alignment emerges through different understandings of value, diverging interests, division of risks and responsibilities, and existing processes and activities that limits actors’ openness to align. Mutual boundary changes are thus necessary in the process of multi-stakeholder engagement in order to enhance organizations’ understanding of value and to capture the envisioned value. This paper functions as an agenda-setting paper, presenting first insights on how the boundary work lens can advance our understanding of alignment processes between focal organizations and their external stakeholders, required for sustainable business model innovation.