Background: Family caregivers are important sources of care for hemodialysis patients. Although caring for a family member is a pleasant feeling, experiencing lots of physical and psychological caregiving burden influences the quality of life among family caregivers of hemodialysis patients. This study aimed to design and validate the quality of life inventory for family caregivers of patients on hemodialysis. Methods: A sequential-exploratory mixed method was conducted in Tehran, Iran, in 2017-2018. In the qualitative phase, the researcher conducted in-depth semi-structured interviews with 19 participants. Finally, a pool of 93 items was extracted from this phase. Then, psychometric properties such as face validity (Impact Score>1.5), content validity ratio (CVR>0.63), content validity index (Item Content Validity Index: ICVI>0.78, Scale Content Validity Index/Average: SCVI/Ave>0.8) and Kappa value (Kappa>0.7, internal consistency (Cronbach’s alpha>0.7), relative reliability (ICC:interclass correlation coefficient),absolute reliability (Standard Error of Measurement: SEM and Minimal Detectable Changes: MDC), convergent validity (Correlation Coefficient between 0.4-0.7), interpretability, responsiveness, feasibility, and ceiling and floor effects were assessed Results: The quality of life inventory for family caregivers of hemodialysis patients was developed with 34 items and five factors (namely patient care burden, conflict, positive perception of situations, self-actualization, fear, and concern). The findings confirm that the scale is acceptable regarding validity, reliability and other measurement features. Conclusions: This inventory is consistent with the health care status in Iran. Therefore, it can be used to measure the quality of life among family caregivers of hemodialysis patients.