The present study identifies the strategies that individuals committed to the cause of Sustainable Investment (SI) use when attempting to persuade institutional investors (e.g., pension funds) to invest in socially and environmentally responsible ways. This article is based on interviews with 15 pioneers of the SI movement in the United Kingdom. Building on the literature on issue-selling, green championship, and corporate social responsibility, this study identifies four tactics that pioneers have employed to "sell" SI in investment institutions: making the business case for SI; forming internal coalitions with mainstream investment professionals; industry networking; gaining credible expertise. The results also suggest that market short-termism and internal organizational contexts dominated by a lack of moral engagement and disempowerment of SI teams are factors that impede champions' efforts. The article opens new avenues for research and recommends ways in which organizational and institutional impediments to SI may be overcome.