The large increase in common institutional ownership raises significant antitrust concerns, even if the precise channel of any potential influence on market outcomes is unclear. Using a novel dataset on shareholders’ board representation, we examine the role of common institutional directors (i.e., joint board representation by institutional shareholders) as one such potential channel with three main findings. First, institutional board representation is extremely low relative to extensive institutional ownership. Second, common institutional directors on rival firm boards are rare. Third, common institutional directors show no incremental effect on market outcomes amidst the positive relationship between common ownership and firm profitability.