Despite cognitive behavioral therapy for insomnia (CBT-I) being effective, barriers to adherence have been documented. Perceived partner alliance has been shown to influence adherence and treatment outcome across a range of other health conditions. The present study examined patients' perceptions regarding the role of their partner in CBT-I and the impact of perceived partner alliance on treatment outcome. Twenty-one patients were interviewed, following CBT-I, to examine the areas where partners were thought to influence the process of CBT-I. The majority of statements made during interviews explicitly mentioned a partner's influence (65%). Additionally, the production of more positive partner statements was associated with better treatment outcome (using the Insomnia Severity Index). The integration of perceived partner alliance into CBT-I is discussed.