Labour Market Intermediaries (LMIs) with a social purpose, or Labour Market Social Innovation, are bubbling since the 1980s due to the fragmentation of labour standards and the growing number of "non-standard forms of work". However, they face an important lack of legitimacy especially in countries like France where labour market is highly regulated. Analysing the legitimation trajectories of two profit-limited LMIs, the Employers' Associations and the Business and the Employment Cooperatives in France, we highlight the role of meta-organisations and some key factors of success and failure. Thus, this article presents some levers that social innovations can use through meta-organizations to gain different types of legitimacy.