BACKGROUND Deficits in cognitive flexibility contribute to impaired functional communication in people with aphasia. Understanding the relationship between functional communication and cognitive flexibility in people with neurologic communication disorders is important. However, traditional methods to assess mental set switching pose significant linguistic, cognitive and motoric response confounds. Eye-tracking methods have great potential to address these challenges. AIMS The goal of this study was to develop and validate an eye-tracking method to index mental set switching in individuals without neurological impairment based upon performance on a nonlinguistic switching task. METHODS Eye movements of 20 adults without communication disorders were recorded as they completed a switching task, requiring participants to match stimuli to one or two search criteria (colour or shape) in single- and mixed-task conditions. Differences between single and mixed conditions were assessed with eye-tracking measures. Performance on the eye-tracking task was compared to standardized measures of cognitive flexibility. RESULTS Eye-tracking measures indexed significant differences between nonswitch and switch trials within and between single- and mixed-task condition. Some standardized assessment measures correlated significantly with the eye movement measures. CONCLUSIONS Results support the construct validity of the novel eye-tracking method for assessing cognitive switching in language-normal adults. Clinical and research implications are discussed.