The purpose of this study is to examine the claim that an infant's ability to respond appropriately to an emotional situation varies according to the emotional state of the mother. Surprise expressions in mother and child were examined both in terms of paralinguistic aspects of surprise vocalizations as well as facial expressions. Seventy-two infants and their mothers (mean age=8 months, range=5–11 months) were video- and audiotaped in their homes. Half of the infants, matched for age and gender, had mothers who reported depressed mood. Infants of mothers with depressed mood showed significantly fewer components of facial expressions of surprise compared with infants of nondepressed mothers. Mothers with depressed mood exclaimed surprise with a significantly lower pitch (mean F0=386.13 Hz) compared to nondepressed mothers (mean F0=438.10 Hz). Furthermore, mothers with depressed mood showed fewer associations between elements of emotional expression than the nondepressed group. Infants' expressions of surprise are influenced by maternal mood, resulting in reduced expression of the emotion in infants of mothers with depressed mood. These results are discussed in terms of coordination of vocal parameters in mother–infant dyadic interaction.