Objective: To test the efficacy of cognitive behavioral therapy for insomnia (CBT‐i) in Parkinsonʼs Disease (PD) and to evaluate its impact on indices of daytime and psychological functioning. Method: Fifteen patients with insomnia disorder (ID) comorbid to PD were enrolled in a single‐case design with multiple baselines. Total wake time, sleep efficiency, and daytime sleepiness were recorded on a sleep diary. Selfreported measures of insomnia, anxiety and depressive symptoms, health‐related quality of life, and psychological variables perpetuating ID were completed. All patients also underwent a clinical interview for ID diagnosis. Results: CBT‐i was associated with significant changes in sleep variables and ID criteria. Significant positive treatment‐ related effects were also noted for all indices of daytime and psychological functioning, and for variables perpetuating ID. All of these improvements were well maintained at 3‐month follow‐up. Conclusion: CBT‐i is a promising therapeutic avenue for patients with PD.