While impact investing was initially reserved for foundations and humanitarian organisations, it has now conquered the world of asset management, which is keen to be part of a useful financial approach. This expansion can be explained by the growing desire of investors to give meaning to their capital in order to participate in sustainable development. The construction of an impact fund gives rise to the implementation of a specific approach to the evaluation of the social and/or environmental impact of projects and to the establishment of new partnerships. Our research work consisted in understanding the way in which the portfolio manager develops a fund likely to be recognised as a genuine impact fund by investors and identifying all the skills that he creates. Even if there are no standard tools for measuring social or environmental impact, the construction of an impact fund allows the manager to acquire specific knowledge and know-how that reinforces his distinctive skills, which are sources of competitive advantage.