The dispute settlement system of the World Trade Organization prides itself on its high degree of judicial independence and the impartiality of its adjudicators. Yet compared to other international tribunals, WTO members exert considerable political control over WTO adjudicators. Contestation over appointments of adjudicators also reflects governments’ awareness that nationality may in fact matter for outcomes. Does it? An empirical analysis of 25 years of Appellate Body activity offers a nuanced answer. Exploiting the random allocation of adjudicators to AB divisions, we find no evidence of systematic national bias looking across the board. Yet we do find evidence of bias for AB chairs, suggesting that when adjudicators are singled out, they become more prone to political pressure. A similar effect pertains to individual dissenting opinions: the presence of a co-national on a division is associated with significantly increased odds of dissent. Judicial independence at the WTO has long been taken for granted. Our findings suggest that such trust is largely warranted, yet that even small tweaks in institutional design increase political pressure on adjudicators, in ways that threaten impartiality. This holds significant implications for WTO reforms going forward.