Over the last few years, public institutions, the market, the financial community and non governmental associations have explicitly demanded that firms improve their environmental performance. However, in spite of the strong pressure from external stakeholders, recent studies have highlighted the fact that only large corporations adopt a pro-active environmental strategy, whereas SMEs tend to comply with external pressures, thus adopting a re-active strategy. In the light of these issues, the paper analyses the stakeholders' role in supporting SMEs' shift from a reactive to a proactive pattern of environmental behavior. In particular, the study seeks to: design a conceptual model which describes stakeholders' “direct role”, i.e. providing SMEs with resources, as well as their “indirect role”, i.e. encouraging SMEs to develop co-operative relationships and creating the necessary conditions for collaboration in improving their environmental performance, and verify empirically stakeholders' actual role in supporting SMEs' environmental development.