Background: Non-cardiac chest pain (NCCP) is common, disabling and costly, yet patients often report feeling dismissed and receive little support. Internet-delivered cognitive behavioural therapy (iCBT) can increase access to care, but little is known about how a therapeutic alliance (TA) is formed when contact is text-based and focused on reinterpreting bodily sensations. Aim: To explore how participants in an iCBT programme for NCCP experienced the TA, and how these accounts align with or challenge established models. Methods: This qualitative study was embedded in a randomised controlled trial of an 8-week iCBT programme targeting cardiac anxiety in NCCP. Twenty-two participants who completed the programme were interviewed using a semi-structured, theory-driven guide based on research on digital alliance. Audio was transcribed and analysed with reflexive thematic analysis, using a deductive, latent approach. Results: Participants described a helpful alliance, experienced as a negotiated process rather than a static quality. Three themes were generated. (1) Agreement on goals and tasks involved “recognising utility” in the programme and balancing personal relevance with sufficient challenge, with the therapist scaffolding this process. (2) The emotional bond centred on the therapist as a “human professional” who combined warmth with structure, responded promptly, and flexibly adjusted tone and intimacy to preferences, including repairing strains in the relationship. (3) Acceptability of the digital medium encompassed modality, platform and content. When these were perceived as secure and trustworthy and, they receded into the background, while a skilled therapist could compensate for shortcomings. Conclusions: The TA in iCBT for NCCP is best understood as a negotiated process in which therapists bridge limitations of digital delivery and support patients’ agency in relation to distressing bodily symptoms. Participants’ accounts underline the importance of attending not only to goals, tasks and bonds, but also to the acceptability of the digital medium when designing online care.