Ethnicity has been shown to shape political, social, and economic behavior in Africa, but the underlying mechanisms remain contested. We utilize lab experiments to isolate one mechanism—an individual’s bias in favor of coethnics and against non-coethnics—that has been central in both theory and in the conventional wisdom about the impact of ethnicity. We employ an unusually rich research design involving a large sample of 1,300 subjects from Nairobi, Kenya; the collection of multiple rounds of experimental data with varying proximity to national elections; within-lab priming conditions; both standard and novel experimental measures of coethnic bias; and an implicit association test (IAT). Our tests find very little evidence of explicit or implicit coethnic bias in the behavioral experiments and IAT. These results run against the common presumption of extensive coethnic bias among ordinary Africans and suggest that mechanisms other than coethnic bias must account for the strong associations we see in the region between ethnicity and political, social and economic outcomes.