Objective To determine the level and influencing factors of informal caregiver burden in gynaecological oncology inpatients receiving chemotherapy. Methods This cross-sectional study enrolled gynaecological oncology patients and their informal caregivers between May 2018 and November 2018 and measured the caregivers' burden using the Caregiver Burden Inventory. The influencing factors were evaluated with univariate regression analysis and multivariate linear stepwise regression analysis. Results A total of 138 patients and their informal caregivers completed the questionnaire. The mean +/- SD total informal caregiver burden score was 53.18 +/- 10.97. The highest mean +/- SD score was recorded in the dimension of time-dependent burden (14.28 +/- 2.74), followed by developmental burden (13.65 +/- 2.15), physical burden (10.52 +/- 2.07), social burden (7.61 +/- 2.58) and emotional burden (7.12 +/- 1.43). Multivariate analysis showed that the informal caregiver's sex, relationship to the patient, daily duration of care, presence of chronic health problems and the duration of the patient's disease were factors influencing the level of caregiver burden. Conclusions The informal caregivers of gynaecological cancer patients hospitalized for chemotherapy experience a moderate level of burden. Nursing measures should be considered to reduce informal caregiver burden and improve the quality of lives of both patients and their caregivers.