The overall objective of this study is to explore the effects of Business Model Innovation efforts put up by Lebanese family firms in transition between second and third generations on the longevity of these firms. Sustainability, inasmuch as it means longevity and prosperity, is a serious problem of high magnitude that family businesses face globally, given the important role that these businesses play in local and world economies. Extensive research has been made on family business and its corporate culture attributes, with focus on change and innovation as key elements of organizational culture. The research covered also Business Model Innovation as an emerging management concept that has critical influences on firms’ success and prosperity. However, the extant research did not address the relation between Business Model Innovation (BMI) and sustainability of family businesses in general, and in Lebanon in particular. To investigate this gap in the literature, a qualitative exploratory approach was used with holistic multiple-case study, where three Lebanese family firms in transition between second and third generations were studied and analyzed individually, and cross-synthesized together. Data was collected through semi-guided interviews, documentation and direct researcher’s observation. The research findings confirmed the positive impact of Business Model Innovation on the sustainability of the studied Lebanese firms. It also validated the researcher’s assumption that the mix of strong culture of family firms and Business Model Innovation will contribute to further success and prosperity of these family firms. These findings have multi-faceted implications on the family businesses, their managers, family business institutes and training institutions. Further research will be needed to expand the scope of the findings, both in theory and geography, and would give further insight to family business about the importance of following modern management concepts like Business Model Innovation, while maintaining the strength of their business culture