Managing customer data in franchise networks is a delicate, complicated and little studied issue. In order to better understand its challenges and the keys to success, this research work offers a study in three stages following the process of grounded theory (Glaser and Strauss, 1967). Thus, a qualitative study was carried out with around thirty franchisors, franchisees and franchise experts. It helped to explore the world of customer data management in franchise networks and to identify its strengths and weaknesses in the context of GDPR (General Data Protection Regulations). The results of the qualitative study helped to clarify our theoretical framework and to position ourselves on the side of the founding theories of the relationship marketing (Morgan and Hunt, 1994). A research model was then defined and tested using a quantitative study administered to a total sample of 192 franchisors and franchisees. Statistical tests carried out show that relational quality, through its determinants (inter-organizational communication, franchisee autonomy, technical and human equipment and the contractualization about customer data management) contributes to achieving positive marketing and commercial performance. Likewise, it has been noted that the collection of customer data cannot be an aim in itself and that it should be accompanied by a real data culture in franchise networks.