The patient-clinician therapeutic alliance is an important aspect of high-quality cancer care. However, components of the therapeutic alliance in adolescents and young adults (AYAs, aged 12-39 years) with cancer have not been defined. To identify components of and barriers to the therapeutic alliance between AYAs, caregivers, and clinicians from the perspective of all key stakeholders. In this qualitative study, semistructured in-depth interviews with patients, caregivers, and clinicians were conducted from 2018 to 2021 with no additional follow-up, with content analysis of resulting transcripts. Participants were recruited from Dana-Farber Cancer Institute, Kaiser Permanente Northern California, Kaiser Permanente Southern California, and an online cancer support community (Cactus Cancer Society). Eligible participants were English- or Spanish-speaking. Eligible patients were aged 12 to 39 years with stage IV or recurrent cancer. Eligible caregivers cared for an AYA living with advanced cancer or one who had died within 5 years. Eligible clinicians routinely provided care for AYAs with cancer. Perspectives on therapeutic alliance. Interviews were conducted with 80 participants: 23 were patients (48% were female; 78% were White), 28 were caregivers (82% were female; 50% were White), and 29 were clinicians (69% were female; 45% were White). The mean (SD) age of patients was 29 (7.3) years. Interviews identified 6 components of therapeutic alliance: (1) compassion; (2) sense of connection; (3) clinician presence; (4) information sharing; (5) shared goals; and (6) individualization of care. While some domains were represented in prior models of therapeutic alliance, a unique domain was identified related to the need for individualization of the approach to care for AYA patients and their caregivers. Interviews also identified potential barriers to building the therapeutic alliance specific to the AYA population, including managing discordant needs between patients and caregivers and communication challenges at the end of life. This study identified core components and barriers to building therapeutic alliance in the AYA advanced cancer population from the perspective of all the key stakeholders in the relationship. A novel component highlighting the need for individualization was identified. This model enables a deeper understanding of how to build therapeutic alliance in the AYA advanced cancer population, which may guide clinician training and facilitate improved care for this vulnerable population.