Abstract : Cancer patients who are undergoing radiotherapy often have many symptoms either due to illness and the effects of radiotherapy so that it can result in family caregiver burden. This study aims to determine the overview of family caregiver burden for cancer patients undergoing radiotherapy. A descriptive quantitative study conducted on family caregivers at the Radiotherapy Polyclinic of Prof. Dr. I.G.N.G Ngoerah Hospital in December 2022. Data were collected using sociodemographic instruments and the Zarit Burden Interview (ZBI) questionnaire, then analyzed using descriptive statistics. In this study, 91 respondents were obtained with the results showing family caregivers expressed their feelings about the intensity of the burden, 35.2% little or no burden, 52.7% mild to moderate burden, and 12.1% moderate to severe burden. Most of them are unmarried children of patients, aged 21 - 30 years, with the most gender male, majority Balinese, average high school education and work as private employees with an average income of below 3 million, the patient's age is 51-60 years, the most common cancer stage is stage 3 with a length of care of 6 months to 12 months. In conclusion, most caregivers experienced mild to moderate burden in caring for their family members with cancer. This study is expected to be a reference for treating palliative doctors team to not only focus on patients but also provide counseling and support to family caregivers of cancer patients who are undergoing radiotherapy.