This study examined the effects of extended Cognitive Behavioral Therapy for Insomnia (CBT-I) on insomnia severity and alcohol use in seven participants using a single-case experimental design. Daily questionnaire data of sleep difficulty and alcohol-related preoccupation served as primary outcomes, with an exploratory look at depressive symptoms, and supplementary measures by the ISI, AUDIT, and DASS-21. Results indicated directional improvements across most participants during treatment, with some maintaining gains at follow-up, though none effect sizes reached statistical significance. Findings provide preliminary support for the potential of extended CBT-I as a treatment for comorbid insomnia and substance use disorders, while highlighting the need for larger controlled studies to establish efficacy.