ObjectiveThis study investigates gender differences in the effect of parents' deaths on sibling tension among bereaved adult children.BackgroundPrevious scholarship on adult sibling relations following the deaths of parents presents inconsistent results. These disparate findings may stem from past studies not taking into consideration the gender of both the deceased parent and the bereaved child.MethodAnalyses are based on three harmonized waves of quantitative and qualitative data collected from 654 adult children nested within 303 families as part of the Within‐Family Differences Study.ResultsMultilevel models revealed that for daughters, but not sons, mothers' deaths in the past 5 years were associated with increases in sibling tension, whereas fathers' deaths did not predict changes in either sons' or daughters' sibling tension, regardless of timing. Qualitative analyses showed marked differences by child's gender in perceptions of patterns of shared work and support surrounding parents' deaths. Typically, sons expressed solidarity with siblings when mothers died and felt that the division of caregiving prior to mothers' deaths and arrangements following their deaths were fair. In contrast, daughters expressed increased solidarity with sisters surrounding mothers' deaths and disdain toward brothers who failed to contribute caregiving, support, or instrumental tasks.ConclusionThese findings underscore how gender of both parents and adult children differentially shape changes in adult children's relationships with their siblings in the face parental deaths, much as they do in other contexts across the life course.