A core proposition in economics is that voluntary exchanges benefit both parties. We show that people often deny the mutually beneficial nature of exchange, instead espousing the belief that one or both parties fail to benefit from the exchange. Across 4 studies (and 8 further studies in the Supplementary Materials), participants read about simple exchanges of goods and services, judging whether each party to the transaction was better off or worse off afterwards. These studies revealed that win–win denial is pervasive, with buyers consistently seen as less likely to benefit from transactions than sellers. Several potential psychological mechanisms underlying win–win denial are considered, with the most important influences being mercantilist theories of value (confusing wealth for money) and theory of mind limits (failing to observe that people do not arbitrarily enter exchanges). We argue that these results have widespread implications for politics and society.