Self-worth protective students characteristically perform well on some occasions yet on other occasions they perform poorly. In this study, two accounts of the poor performance of self-worth protective students are assessed. The first is that their poor performance is an outcome of evaluative threat. The second is that their poor performance is an outcome of future outcome uncertainty: a product of their uncertain global self-esteem and uncertainty about the causes of achievement outcomes. Students high or low in self-worth protection were exposed to either noncontingent success (creating future outcome uncertainty), noncontingent failure (evoking evaluative threat), or contingent success. Their ability to solve two tasks that involved a high degree of uncertainty was then assessed. Students high in self-worth protection performed poorly following both noncontingent failure and noncontingent success, supporting the roles of both evaluative threat and future outcome uncertainty. The implications in terms of enhancing the achievement of students high in self-worth protection are discussed. (Contains 3 tables.)