PurposeThis article analyses how the MONDRAGON Group has overcome the barriers that the literature identifies in the creation of employee owned companies (Mygind and Poulsen, 2021), and how it has managed to grow over the last few decades.Design/methodology/approachTo this end, based on an analysis of the legislative framework and the internal documentation of the MONDRAGON Group and its cooperatives, the case of what is often considered the most successful and highly developed network of co-operative firms is studied.FindingsThe study leads us to conclude that MONDRAGON has had sufficient capacity to overcome the barriers faced by worker-owned companies and has known how to adapt to the economic and social demands of each moment, despite the fact that at certain times it has had to act flexibly in its principles.Research limitations/implicationsThe work is limited to the analysis of the Group's internal documentation. It would be interesting to complement this vision with the perceptions of MONDRAGON's partners.Practical implicationsThe MONDRAGON Group's study can show other cooperative experiences what the keys to success are.Originality/valueMONDRAGON has been analysed from different perspectives, but how it has overcome the specific barriers presented by employee-owned companies has not been specifically studied. This perspective makes it possible to identify some of the group's success factors.