Innovation processes are increasingly spreading through the unbounded universe of European small and medium enterprises (SMEs). It represents a fundamental opportunity especially for those SMEs operating in the so-called ‘green economy’ sectors, in order to be competitive in a National, European and International market with their sustainable products and services. Drawing upon a database of over 300 enterprises operating within the eight defined green sectors, this paper assesses the determinants and drawbacks of innovation. In particular, by using an econometrical approach, we tested the following propositions: (1) small dimension of enterprises is not an obstacle to their innovation capabilities; (2) the adoption of an internationalisation strategy is an opportunity and a stimulus to innovation for SMEs; (3) cooperation with research centres, financial partners, trade association and public entities can help SMEs to overcome difficulties and help them to develop and offer innovative products and services, so to be competitive at an international level. The econometric analysis shows a positive impact of the variables ‘dimension’ and ‘level of internationalisation’ on innovation capabilities. In addition, cooperation with research centres and access to capital market are positively related with effective innovations.