Many moderators of the EO-P relationship have been previously identified, but research on management-related factors conducive to EO effectiveness remains insufficient. In particular, no scholar asked whether the effectiveness of EO is facilitated or hampered by a family management (FM). FM can be referred both to the percentage of managers who are family members (PMFM) and to the number of generations involved in management (NGI). In this research we seek to explore how PMFM and NGI influence the EO-P relationship. Drawing on the agency (Jensen and Meckling, 1976; Schulze et al., 2001) and the upper echelon theories (Hambrick & Mason, 1984), we theorize and empirically test that the more a family is involved in the management of the firm, the lower EO effectiveness. In other words, we test that both PMFM and NGI play the role of negative moderators of the EO-P relationship.