Research in psychology and neuroscience suggests that facial mimicry plays a causal role in understanding facial expression of emotion. Accurate understanding of facial emotion, in turn, grounds emotional development. Are pacifiers, which disrupt facial mimicry in the user, associated with compromised emotional development? We examined facial mimicry in children and found that duration of pacifier use was associated with reduced facial mimicry in boys. In two questionnaire studies of young adults, pacifier use also predicted lower perspective taking and emotional intelligence in males. Pacifier use did not predict these emotion processing skills in girls. Future confirmatory studies are proposed.