Studies on determinants affecting child development are still limited in Greece. The aim of the present study was to describe the socio-demographic characteristics associated with neurodevelopment in infants aged 18 months in the Mother-Child Cohort (Rhea Study) in Crete, Greece. A total of 599 (72.9%) mothers agreed to participate in the neurodevelopment protocol and 612 infants (586 singletons and 26 twins) were assessed by means of the Bayley Scales of Infant and Toddler Development (3rd edition). The present analysis includes 605 infants. Multivariable linear regression models were implemented to examine the associations between the Bayley-III standardised scores and different parental and infant characteristics, also adjusting for quality of assessment. Girls were found to have better neurodevelopmental outcomes in cognitive, receptive and expressive communication, fine motor and social-emotional development. Maternal higher education was positively associated to almost all aspects of infant neurodevelopment assessed. Increasing number of older siblings was negatively associated with cognitive development, communication skills and gross motor development. Our results, also, suggest a positive effect of maternal employment on infants' receptive and expressive communication, and gross motor scores. The results of the present study suggest that in the population on Crete social and environmental factors contributed more to infants' neurodevelopment at 18 months than biological factors.