Anxiety has a disruptive effect on performance in a number of domains. The purpose of this study was to determine whether individual differences in working memory (WM) capacity are related to an individual's susceptibility to anxiety's detrimental effect on performance. Fifty undergraduate students (28 females) were administered the State-Trait Anxiety Inventory (STAI) (Spielberger, Gorsuch, Lushene, Vagg, & Jacobs, 1983) to measure trait anxiety and the automated operation span task to measure WM capacity (Unsworth, Heitz, Schrock, & Engle, 2005). Then, they performed a highly demanding dual-task that consisted of a primary short-term memory task and a secondary tone-discrimination task that served as a measure of spare capacity. Anxiety and WM capacity interacted to affect performance on the auditory task so that those low in WM capacity were particularly vulnerable to anxiety's disruptive effect, whereas those high in WM capacity were buffered against anxiety's effect. These findings suggest that WM capacity may be an important factor in determining which individuals underperform on anxiety-provoking tests such as scholastic achievement tests.