The influence of the owner-family over Family-Owned Business performance issue has received recent research attention. Fewer are the amount of research devoted to analyse the owner-family effect over firm’s managerial capabilities (MC). This paper contributes to this vein of research analysing a sample of Spanish SME-FOB. It contributes differentiating family involvement depending on the organizational role and making a whole consideration of MC. Also it considers family complexity. Results show that family involvement produces a negative impact over MC. However it turns positive when ownership-management roles are differentiated and proper family governance structures deployed. Two findings should be highlighted: family complexity appears as extremely harmful for MC, and family governance structures only increase MC when it fit with the level of family complexity, in other case, an oversized family governance structure damages MC.