Abstract: Family businesses account for a great proportion of businesses worldwide which makes them of interest for many researchers. Despite considerable research in this area, however, there is little empirical evidence for the claim that family involvement and institutionalization simultaneously affect trust among family members in the family business context. To address this knowledge gap, the researcher investigated the effects of these two subjects on intra-family trust through a pilot study and a primary research examining family businesses in all organized industrial zones within the city of Istanbul, Turkey. The researcher’s overall effect expectation was partly answered as the results indicated that some, but not all institutionalization and family involvement factors affected intra-family trust in the context of family businesses. Moreover, these effects were mixed-they were associated with different issues. Top decision-making, especially with the presence of deadlocks, was found out to affect intra-family trust negatively, suggesting that this issue was perceived to be of a higher priority than the trust among family members. Very similar results were reached if the issues were the selection of the next top manager or people to hire. Opposite-positive-effects were witnessed when issues such as succession planning, inter-generational knowledge transfer, employed family member orientation and family members’ loyalty towards the business were considered. Implications of the study’s findings and suggestions for future research were presented; keeping in mind that besides being limited in many ways, this article was a pioneer in terms of the relationship investigated.