Purpose The purpose of this article is to provide a comprehensive understanding of the roots of family firms' competitive advantages by defining and testing the familiness learning mechanisms that emerge from the interaction between family and firm. Because family members are economically, emotionally and socially attached to the firm, family firms are expected to be able to develop unique and difficult to imitate learning mechanisms related to family firm value creation. Design/methodology/approach This study operationalizes and tests the concept of the familiness learning mechanism using a sample of nonlisted Spanish family firms. The sample is analyzed using the structural equation modeling method. Findings Results show that family firms' ability to accumulate internal and external knowledge, integrate social knowledge, as well as create and retain socioemotional knowledge forms the concept of the familiness learning mechanism, and the authors show what implications it might have for family firm value creation. Originality/value By using the dynamic capabilities approach, this article highlights the importance of the knowledge and learning derived from family involvement in the firm. The creation of learning mechanisms occurs because of the close relationships between family members and their simultaneous participation in the family and in the company systems, which creates a unique context wherein knowledge and learning emerge in an idiosyncratic manner.