In this paper, we study the effects of business culture on market efficiency. We exogenously vary the type of business culture between business-is-business cultures, which consist on impersonal relationships where financial matters are paramount, and business-is-family cultures, which comprise of cohesive personal relationships where financial matters and personal attachments are intertwined. We use a laboratory experiment to assess the effect of business cultures in environments with different degrees of contract enforceability and competition. Our main results indicate that business-is-family cultures are more effective when contracts are unverifiable because they help market participants overcome problems of trust. On the other hand, we find that business-is-business cultures are more effective in competitive settings because they facilitate the severance of ties with unproductive partners.