Digital–sustainable co-transformation requires organisations to tackle digital- and sustainability transformation as one strategic concern. While digital technology can support sustainability transformation, its production, use and end-of-life also has negative sustainability impacts. How can organisations manage this digital sustainability dilemma when conducting co-transformation? This case study provides learnings from Greenpeace's digital transformation as an example of digital–sustainable co-transformation. The key insights show that co-transformation means balancing value-tensions of digital sustainability among four co-transformation dimensions: environment, social, economic and technology. We provide learnings about how the non-governmental organisation managed these tensions, which can support organisations in championing their own co-transformation.