This study aimed to describe informant discrepancies between mother and father reports of child vulnerability in youth with spina bifida (SB) and examine variables that were associated with these discrepancies. Ninety-two parent dyads, with a child with SB (ages 8-15 years), were recruited as a part of a longitudinal study. Mothers and fathers completed questionnaires assessing parental perception of child vulnerability (PPCV), as well as medical and demographic information, behavioral aspects of the couple relationship, parenting stress, mental health of the parent, and child behavioral adjustment. The degree to which there was a parenting alliance was assessed with observational data. Mother-father discrepancies were calculated at the item level. Findings revealed that greater father mental health symptoms, parenting stress, and child behavior problems were associated with "father high and mother low" discrepancies in PPCV. There were also lower scores on observed parenting alliance when there were higher rates of "father high and mother low" discrepancies in PPCV. For families of youth with SB, discrepancies in PPCV where fathers perceive high vulnerability and mothers perceive low vulnerability may be a "red flag" for the presence of other parental and child adjustment difficulties. Findings are discussed in terms of the Attribution Bias Context Model and underscore the importance of including fathers in research on families who have children with chronic health conditions.