In recent years, in addition to financial and social objectives, the microfinance industry has started to look at its environmental bottom line. The objective of this paper is to identify why microfinance institutions decide to go green. Data was collected through a quantitative survey of 160 MFIs and qualitative semi-structured interviews of 23 MFIs’ top managers. Basing our analysis on the model of ecological responsiveness developed by Bansal and Roth :717–736, 2000), we discover that MFIs for which legitimation is the (...) dominant driver tend to adopt a defensive approach and set up more superficial negative strategies to appear green. In contrast, MFIs for which social responsibility is the dominant driver tend to be more proactive and innovative and develop adapted financial and non-financial services to promote environmentally friendly practices. (shrink)