In this research the empirical case of the “Partnership for Sustainability”, a long-term partnership between a major player in the German grocery retail industry and one of the biggest environmental organizations in Germany, was explored in order to gain an understanding of organizational learning processes within non-profit and business collaborations towards sustainability. Using existing theoretical concepts about organizational learning and sustainability in the field of cross-sectoral collaboration these fields of research are brought together. As a result, organizational learning processes within the non-profit and between the partnering organizations were identified and the associated learning results were pointed out. Therefore, essential changes and adaptations in the Partnership for Sustainability could be explored throughout the years of the collaboration. Furthermore, the contribution of organizational learning processes to a cross-sectoral collaboration has been illuminated.