American politicians repeatedly and strenuously invoke concerns about fairness when pitching their trade policies to their constituents, unsurprisingly since fairness is one of the most fundamental and universal moral concepts. Yet studies to date on public opinion about trade have not been designed in such a way that they test whether fairness is important, nor whether the mass public applies fairness standards impartially. Drawing on findings in social psychology and behavioral economics, we develop and find evidence for an “asymmetric fairness” argument. In a national survey of Americans, we find strong evidence that fairness, conceived in terms of equality, is crucial for understanding support for potential trade deals and support for renegotiating existing ones. Americans view as most fair and most preferable outcomes in which concessions and benefits are equal across countries, especially when those equal benefits match productivity. However, we find that Americans have an egoistically biased sense of fairness, responding particularly negatively to any outcome that leaves the United States relatively worse off—a sense of injustice that does not extend to the same degree to relative gains for Americans.