Background: Poor sleep quality is a common problem in pregnant women, however there is scarce research evidence regarding the association between maternal perinatal insomnia and later social-emotional child development.Participants: This study is part of the Akershus Birth Cohort, a longitudinal population-based study. Birth record and questionnaire data of 1,346 women were used.Methods: Maternal symptoms of insomnia were measured at pregnancy week 32 and at eight weeks postpartum and social-emotional child development was assessed at two years of child age. Correlational and multiple linear regression analyzes were performed.Results: Both, pre- and postnatal symptoms of insomnia were significantly correlated with poorer social-emotional child development two years later (r = 0.09, p < .01 and r = 0.13, p < .001). Adjusting for potential confounding factors, the prospective effect of maternal symptoms of perinatal insomnia on social-emotional child development remained significant in the multiple linear regression analyzes (β = 0.08, p < .01 and β = 0. 10, p < .01).Conclusions: We found a prospective effect of maternal symptoms of perinatal insomnia on social-emotional child development, highlighting the potential relevance of both pre- and postnatal maternal sleep for later social-emotional child development. Future studies ought to examine the bio-psycho-social mechanisms and implications of poor maternal sleep in the perinatal time in more detail.