BACKGROUND: Cancer among young adults (18-39 years) is relatively rare, but remains a leading cause of disability, morbidity, and mortality. Identifying strategies to support young adults' health following a diagnosis of cancer is important. Yoga may enhance health and could be delivered by videoconference. However, little research exploring yoga, and no research exploring videoconference delivery of yoga has been conducted with this cohort. We worked with young adults affected by cancer and developed, piloted, and refined a yoga intervention delivered by videoconference. OBJECTIVE: To evaluate our yoga intervention in a full-scale, mixed methods, single-arm, hybrid effectiveness-implementation trial. METHODS: Young adults 18 years or older, diagnosed with cancer between the ages of 18-39 years of age, and at any stage along the cancer trajectory are eligible. Participants receive 2 yoga classes/week over 12-weeks by videoconference and complete assessments at baseline, post-intervention, and 6- and 12-month follow-ups. Assessments include self-reported questionnaires (ie, stress, yoga barriers, physical activity behaviour, fatigue, cognition, cancer-related symptoms, general health, health-related quality of life, self-compassion, mindfulness, group identification), physical assessments (ie, aerobic endurance, flexibility, range of motion, balance, functional mobility), and a semi-structured interview (post-intervention only; exploring perceptions of acceptability, feasibility, and experiences). Quality improvement cycles occur every 6 months. Repeated measures analysis of variance will be conducted to explore effectiveness, descriptive statistics and responder/non-responder analyses will be used to explore implementation, and qualitative interview data, analyzed using content analysis and reflexive thematic analysis, will bolster effectiveness and implementation findings. DISCUSSION: As the first full-scale trial to evaluate yoga delivered by videoconference for this cohort, findings will make substantial contributions to young adults' supportive cancer care. CONCLUSION: This protocol, reporting on yoga delivered by videoconference for young adults diagnosed with cancer, will enhance transparency and reproducibility and provide a reference for forthcoming trial results. TRIAL REGISTRATION: NCT05314803 at clinicaltrials.gov.