Purpose: Adolescents and young adults (AYA) with cancer present a unique challenge to health care institutions. Their cancer diagnosis and treatment have a profound impact upon their health and well-being. Despite the various support services aimed at improving their quality of life, their needs and preferences are often underestimated or misjudged. Recent studies show that patients are empowered by the knowledge and support they receive online. Given the extensive use of social media among AYA, we aim to identify promises, challenges, and recommendations for integrating these platforms in AYA cancer care. Methodology: We systematically searched seven databases systematically: Scopus, PubMed, PsycInfo, Web of Science, CINAHL, SocINDEX, and Media. We placed no restriction on the type of methodology used in the studies. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was used to frame the research. Results: Many studies argued that health care professionals need to integrate social media in their clinical practice to engage with patients' lifeworld. Social media were considered important allies in optimizing cancer care at all levels of support, ranging from information provision, treatment adherence, diet and exercise interventions, to professional, peer, and psychosocial self-care. Lack of research on the efficacy of social media in the context of psychosocial support was a commonly cited problem. A small number of publications paid attention to the inherent risks of promoting self-care online. Conclusion: Future studies should continue to pursue empirical research on the efficacy of online psychosocial care, while not neglecting the ethical challenges of social media research.