Research has explored the organizational context required to develop sustainable brands, but has ignored how the transformation unfolds. We draw on the internal branding conceptual framework to study how sustainable brand transformation is internally managed and the issues emerging in this transformation. A qualitative study, based on a variety of sources (interviews with managers, observation, secondary data), reveals collaborative and tensed internal branding dynamics between corporate social responsibility (CSR) and marketing managers, inducing a CSR-based positioning and co-creation of sustainable brands. The figure of the activist emerges as a leader who works to turn his colleagues into sustainable brand-change champions. Moreover, when connecting to external branding, managers navigate through two sets of contradictions that feed brand dilemmas: transparent communication versus opaque silence and self-confidence versus doubt. Theoretical contributions in internal branding, brand co-creation, and sustainable brand complexities as well as recommendations to internally manage and accelerate sustainable brand transformation are presented.