Background: Cancer has a major impact on the lives of family caregivers, including their health and quality of life (QOL). However, little is known about the QOL of family caregivers of adult cancer patients in Ethiopia. This study aimed to assess the QOL and associated factors among primary family caregivers of adult cancer patients in Addis Ababa, Ethiopia.; Methods: In this cross-sectional study, 291 family caregivers completed the survey in the Amharic language. The Caregiver Quality of Life Index-Cancer (CQOLC) was used to measure QOL of family caregivers. Descriptive and linear regression analyses were conducted using SPSS version 23.; Results: The mean age of the family caregivers was 37.04±11.47 years and 51.5% were male. The mean score of QOL was 82.23 (±16.21). Not being employed in private sector ( β = -0.128; CI=-7.82, -0.45; p = 0.028), having family monthly income less than 16 USD ( β = 0.132; CI=0.87, 10.88; p = 0.021) and not having family monthly income greater than 64 USD ( β = -0.128; CI= -10.43, -0.66; p = 0.026), being spouse ( β = 0.179; CI: 1.34, 11.99; p = 0.019) and not residing in urban areas ( β = -0.139; CI: -10.53, -0.96; p = 0.019) were negatively associated with the QOL of the family caregiver and explained 8.7% of the variation ( R 2 =0.087; p =0.000).; Conclusion: Our findings identified factors such as occupation, income, relationship with the patient, and place of residence that negatively associated with the QOL of family caregivers. Targeted interventions such as social and economic support and bringing the care to the patient's residence place are needed to improve the QOL of family caregivers of adult cancer patients.