Background: Cancer is one of the most common diseases in children. Cancer in children can cause many problems for parents, and impose heavy care burden on them, which can lead to negative health consequences. The aim of this study was to determine caregiving burden and relevant influential factors among parents of children with cancer. Materials and Methods: This cross-sectional descriptive study was done on 125 parents of children with cancer in oncology department of Shohada Hospital, Tehran, Iran, during March to August 2017. Caregiving burden was measured using the Caregiver Burden Scale. Descriptive statistics, independent-samples T test, one-way ANOVA, Pearson’s correlation analysis, and multivariate linear regression analysis (stepwise method) were used in data analysis with SPSS software (v.19). Results: The mean score of parents’ care burden was 52.76 ± 10. Moreover, 17.6%, 71.2% and 11.2% of parents had low, moderate, and high care burden, respectively. Regression analyses indicated that the factors associated with care burden were cancer type (Acute myeloid leukemia (β=0.36, p<0.001) and Ewing sarcoma (β=0.16, p=0.007)), the number of hospitalization (β=0.38, p<0.001), duration of disease (β=-0.31, p<0.001), parent’s age (β=-0.29, p<0.001), parent’s income (β=-0.23, p<0.001), and child’s age (β=0.24, p<0.001). These variables accounted for 65% of the variance in care burden. Conclusion: The result of this study demonstrated that most of parents of children with cancer had moderate levels of care burden. Different variables increased care burden in parents. Therefore, planning for holistic interventions to reduce care burden in parents and improve quality of care is necessary.