Prenatal symptoms of depression in mothers are associated with infants' emotional reactivity. Context-incongruent reactivity, comprising mismatches between the eliciting context and emotional reactions, predicts negative long-term socioemotional outcomes in children. However, the etiology of context-incongruent reactivity is largely unknown, obscuring a full understanding of its potential role as a vulnerability in models outlining the transmission of risk for emotion difficulties from mothers to offspring. We tested mothers' (N = 92) prenatal depressive symptoms as prospective predictors of infants' context-incongruent emotion. Greater prenatal symptoms predicted more context-incongruent negativity in infants even when controlling for context-congruent affect. Findings demonstrate a novel utility of context-incongruent emotion as one possible vulnerability linking mothers' prenatal depression to socioemotional difficulties in offspring. (PsycInfo Database Record (c) 2024 APA, all rights reserved).