We examine whether corporate culture limits insider trading profitability. Using textual analysis of firms’ 10-K filings, we construct culture measures mapped to the Competing Values Framework (CVF) of Cameron et al. (2008), which classifies corporate culture into external culture, consisting of create culture and competition culture, and internal culture, consisting of collaborative culture and control culture. Firms with external cultures are likely to be more market-oriented and attentive to investor demands in order to safeguard their reputation and attract resources to the firm. Therefore, we argue that firms with higher levels of external culture will try to restrict insiders’ access to and/or ability to exploit their private information to boost investor confidence and increase their willingness to invest in the firm. Consequently, we anticipate a negative relationship between external culture and insider trading profitability. Using a large US sample from 1995 to 2020, we find that an externally oriented corporate culture is associated with significantly lower insider trading profitability. Mechanism tests indicate that this effect is partly mediated through a better market information environment (e.g., narrower bid-ask spreads). The effect is more pronounced when outside monitoring, as proxied by low analyst coverage, is weak. This finding is consistent with external culture substituting for external monitoring in limiting insiders’ rents.