AbstractAntenatal exposure to maternal stress is a factor that may impact on offspring cognitive development. While some evidence exists of an association between maternal antenatal depressive or anxiety symptoms and infants' cognitive outcomes, less is known about the role of biological indices of maternal antenatal stress in relation to infant cognitive development. The current study investigated the association between maternal depressive and anxiety symptoms, stress and inflammatory markers during pregnancy and infant's cognitive development in a sample of 104 healthy pregnant women (mean gestational age = 34.76; SD = 1.12) and their 12‐week‐old infants (mean postnatal weeks = 11.96; SD = 1.85). Maternal depressive and anxiety symptoms were evaluated during pregnancy, alongside measurements of serum Interleukin‐6 (IL‐6), C‐Reactive Protein (CRP), salivary cortisol, and alpha amylase (sAA) concentrations. Infant cognitive development, maternal caregiving and concurrent anxiety or depressive symptoms were assessed 12 weeks after delivery. Hierarchical linear regressions indicated that higher maternal diurnal cortisol and CRP levels were independently associated with lower infant cognitive development scores, while adjusting for infant gender and gestational age, maternal IQ, caregiving, depressive, or anxiety symptoms. Though correlational, findings seem suggestive of a role for variation in maternal biological stress signals during pregnancy in influencing infants' early cognitive development.