Background: Relational autonomy is an alternative concept of autonomy in which an individual is recognized as embedded into society and influenced by relational factors. Social context, including social location, political structure, and social forces, significantly influence an agent to develop and exercise autonomy skills. The relational approach has been applied in clinical practice to identify relational factors impacting patient autonomy and decision-making, yet there is a knowledge gap in how these factors influence the demonstration of relational autonomy in the context of medical decisions of adults. Objective: The present study targeted the existing knowledge of what and how relational factors impact individuals making medical decisions using the theoretical framework of relational autonomy. Methods: A meta-synthesis study was utilized. Four electronic databases, including Embase, OVID Medline, CINAHL, and PubMed, were searched, along with gray literature and reference lists, to identify relevant studies. Results: 23 studies reporting 21 qualitative and two mixed-method studies were reviewed. Four themes emerged from the qualitative findings: (1) supportive relationships facilitate an individual’s relational autonomy; (2) obtaining comprehensive information from broader sources helps individuals exercise relational autonomy; (3) undue family pressure impedes the exercising of patient relational autonomy; and (4) healthcare providers’ dominant voice hampers the demonstration of relational autonomy. Conclusions: Applying relational autonomy to assist adults in making well-considered decisions is essential. The meta-synthesis suggests establishing a supportive relationship between individuals, healthcare providers, and family. A supportive relationship will allow healthcare providers to make judgments in line with an individual’s values and wishes with the aim of promoting relational autonomy. Advance care planning was proposed as the effective solution to obtain a consensus between individuals and their families while respecting an individual’s values and preferences. Furthermore, it is considered crucial for healthcare providers to appreciate an individual's values and incorporate their preferences into recommendations.