Background <p>Survivors of oesophageal and gastric cancer frequently experience persistent symptoms and functional limitations that affect their health-related quality of life (HRQL). Although self-care is increasingly recognised as a central component of survivorship care, little is known about what determines self-care engagement or whether engagement is associated with better HRQL. This study examined the sociodemographic and healthcare-related variables associated with self-care engagement and explored its association with global quality of life (QOL) in a nationwide cohort.</p> Methods <p>A cross-sectional survey was conducted among individuals diagnosed with oesophageal or gastric cancer in Sweden between 2021 and 2023. Participants completed the EORTC QLQ-C30 and a study-specific questionnaire assessing symptoms and self-care. Self-care engagement was operationalised as the ratio of self-care strategies used to the number of symptoms experienced and categorised into no, moderate, and high. Factors associated with self-care engagement were analysed using multinomial logistic regression, and the association between self-care engagement and global QOL was assessed using linear regression, adjusting for sociodemographic and clinical confounders.</p> Results <p>Of the 432 respondents, 422 reported at least one symptom and were included in the self-care analysis. One-third of the participants reported no self-care engagement, whereas two-thirds reported moderate or high engagement. Across all models, university education was the strongest and only consistent variable associated with self-care engagement (high vs. no self-care engagement: odds ratio 2.83, 95% confidence interval 1.48–5.42). Neither assignment of a designated contact nurse nor proximity to the treating hospital was associated with self-care engagement. Participants with high self-care engagement had substantially better global QOL than those with moderate or no self-care engagement, with mean differences exceeding 10 points on a 0–100 scale. Global QOL did not differ between the moderate and no self-care groups.</p> Conclusions <p>Self-care engagement varies widely among oesophageal and gastric cancer survivors and appears to be influenced by educational level. High self-care engagement is associated with clinically meaningful improvements in global QOL, whereas no or moderate self-care appears insufficient to confer benefits. These findings suggest an equity gap in survivorship care, and future research should explore the development of structured and accessible interventions to enhance self-care capabilities among patients with lower educational attainment.</p>