Aims and Objectives: To investigate the factors influencing caregiver burden in families of hospitalised lung cancer patients.; Background: Even though cancer symptoms among hospitalised lung cancer patients are serious and negatively affect caregivers, few research regarding to the factors of caregiver burden in hospitalised lung cancer patient has been carried out.; Design: Cross-sectional, descriptive and correlational study.; Methods: A convenience sample of hospitalised lung cancer patients (n = 107) was recruited from K University hospital in South Korea. Family depression, social support and caregiver burden as well as patients' lung cancer symptoms were measured using peer-reviewed and standard measurement tools. Descriptive statistics and parametric tests including stepwise regression were used to analyse the data. The STROBE guideline has been used to report this study.; Results: Caregiver burden among the families of hospitalised lung cancer patients was high; the regression model for caregiver burden among participants' families was significant. Depression among families was found to be the most influential factor for caregiver burden, followed by patients' lung cancer symptoms.; Conclusions: This study revealed that family caregivers' depression and patients' lung cancer symptoms were the most significant factors for families' caregiver burden. Future research should be conducted to identify the causes of depression among families of hospitalised lung cancer patients and develop management programmes to address such causes. It is also necessary to investigate the causes of increased caregiver burden that differentiate families of lung cancer patients from other cancer patients and provide education to help such families understand such causes.; Relevance To Clinical Practice: Findings from this study show that family's depression and lung cancer symptoms were significant factors for caregivers' burden. Hence, it is suggested for the healthcare providers to find for the best solution/strategies to reduce the caregiver's burden.