Acute stress has frequently been shown to impair cognitive flexibility. Most studies have examined the effect of stress on cognitive flexibility by measuring how stress changes performance in paradigms that require participants to switch between different task demands. These processes typically implicate pFC function, a region known to be impaired by stress. However, cognitive flexibility is a multifaceted construct. Another dimension of flexibility, updating to incorporate relevant information, involves the dorsal striatum. Function in this region has been shown to be enhanced by stress. Using a within-subject design, we tested whether updating flexibility in a DMS task would be enhanced by an acute stress manipulation (cold pressor task). Participants' cortisol response to stress positively correlated with a relative increase in accuracy on updating flexibility (compared with trials with no working memory interference). In contrast, in line with earlier studies, cortisol responses correlated with worse performance when switching between trials with different task demands. These results demonstrate that stress-related increases in cortisol are associated with both increases and decreases in cognitive flexibility, depending on task demands.