In 2015, there was an increase in cases of congenital malformations in newborns in Brazil, associated with maternal Zika virus infection, having serious social and economic repercussions for the families. The study aimed to estimate the prevalence of catastrophic expenditure by families of children with severe or mild/moderate congenital Zika syndrome (CZS) in comparison to families of children without a diagnosis of CZS in the state of Rio de Janeiro. Catastrophic expenditure occurs when spending exceeds a given proportion of the family income due to a disease. Family caregivers of children with severe CZS were younger and had less schooling and lower income. Prevalence of catastrophic expenditure was higher in families of children with CZS. Among caregivers of children with severe CZS, the prevalence of catastrophic expenditure was higher in those with severe or very severe depression, anxiety, and stress. Low social support among caregivers was also a determinant factor for increased prevalence of catastrophic expenditure. The burden on caregivers of children with severe CZS exacerbates a situation of vulnerability that requires the expansion of mechanisms for financial and social protection, through linkage of various policies capable of effectively reaching this group.