Objective: Tourette syndrome (TS) can be associated with cognitive dysfunction. We assessed a range of cognitive abilities in adults with TS without comorbid disorders. Method: Participants completed tests of sustained attention, verbal and non-verbal reasoning, comprehension, verbal fluency, working memory, inhibition, and set-shifting. We compared patients’ task performance with that of healthy controls, and evaluated relationships between cognitive abilities and symptoms of obsessive-compulsive disorder (OCD), ADHD, impulse control problems, and mood disorders. Results: Patients with TS exhibited impairments on four measures assessing response inhibition, fine motor control, set-shifting, and sustained attention. The Wisconsin Card Sorting Test (WCST) discriminated best between patients and controls. Patients’ deficits were not correlated with tic severity or symptoms related to OCD, ADHD, or mood disorders. Conclusion: Deficits on the WCST could constitute a neurocognitive endophenotype for TS, reflecting dysfunction within neural networks involving basal ganglia, pre-supplementary motor area, and inferior prefrontal regions.