<p>Recent research highlights the link between poor sleep and emotion regulation difficulties. However, few studies have investigated emotion regulation changes following cognitive behavioral therapy for insomnia (CBT-I), the first-line treatment. In this quasi-experimental study, fifteen patients with chronic insomnia undergoing a 6-week CBT-I program at the National Institute of Mental Health, Czech Republic (NIMH-CZ), were compared to fifteen matched controls continuing treatment as usual. Both groups completed self-report measures of emotion regulation difficulties, insomnia severity, and hyperarousal at baseline and after six weeks. Due to residual group differences, age was included as a covariate. CBT-I significantly reduced insomnia severity compared to controls, but no large impact was observed in emotion regulation difficulties or hyperarousal owing to treatment. However, these results show only preliminary indicators that emotion regulation difficulties remain relatively intact after treatment and no firm conclusion can be drawn due to limits of this study. Findings therefore require scrutiny in larger samples. Further research is warranted to understand the mechanisms underlying therapeutic change in insomnia treatment.</p>