Background <p>Genomic medicine increasingly depends on patients’ willingness to share genomic and medical data. While data sharing supports advances in personalised care, it also raises ethical and social concerns related to privacy, trust and participation. Understanding these factors requires attention to patients’ health literacy and their capacity to interpret and act upon genomic information.</p> Methods <p>A systematic review was conducted according to PRISMA guidelines to identify empirical studies published between 2015 and 2025 that explored patients’ understanding of genomic information and their willingness to share data. Searches were performed in PubMed, Web of Science and Scopus. Eligible studies included qualitative, quantitative and mixed-methods designs. Findings were synthesised thematically and Nutbeam’s model of health literacy was used in the discussion to interpret the results.</p> Results <p>Fifteen studies met the inclusion criteria. Participants demonstrated basic understanding of genetic terms but limited knowledge of data infrastructures and governance. Trust was a central factor influencing willingness to share data, often compensating for limited genomic literacy. Moral and altruistic motives encouraged engagement, whereas financial considerations played a minor, context-dependent role.</p> Conclusions <p>Data sharing in genomic medicine relies on more than factual knowledge. Strengthening health literacy through transparent, dialogue-based, and participatory approaches can promote informed, autonomous, and ethically responsible participation in genomic research.</p>