Background: Effectiveness of cognitive behavioural therapy for insomnia (CBT-I) has not been explored in Chronic Fatigue Syndrome (CFS), a condition where disturbed sleep is a principal symptom. This study aimed to report feasibility, acceptability and initial effectiveness of CBT-I in CFS. Methods: Sixteen individuals with CFS received face-to-face CBT-I. Treatment comprised six sessions of sleep education, hygiene, restriction, stimulus control and cognitive therapy and completion of daily sleep diaries with an overarching aim to establish regularity in sleep-wake patterns. Patients completed self-report questionnaires (fatigue, pain, mood, sleep preoccupation, insomnia severity, and dysfunctional beliefs about sleep) pre- and post-treatment. Results: Of the seven who completed the intervention five improved on self-reported sleep parameters (diary measures of sleep onset latency, awakenings during the night) following treatment. However, CBT-I was not acceptable for all (56%). Total fatigue (Chalder Fatigue), dropped from mean 22 to 16. Those not able to complete the intervention had higher fatigue, pain, depression and anxiety and reported more severe insomnia at baseline compared to completers. Conclusion: CBT-I is an acceptable non-pharmacological approach with potential to treat sleep disturbances in some CFS patients. Strategies to reduce attrition and increase adherence are necessary, possibly telephone or online sessions, for this group.