While insomnia symptoms may be a risk factor for mental disturbances, few studies evaluated “Insomnia Disorder” and its relationship with perinatal psychopathology. Pregnant women were recruited during their last routine assessment before being hospitalized for delivery during the 3rd trimester at the Gynaecological Unit of the University Hospital of Ferrara and Udine, Italy, from January 2022 to January 2023. Our assessment included baseline evaluation (T0), and evaluations at 1 month (T1) and 3 months (T2) in the postpartum period, with specific questionnaires for insomnia disorder, such as Sleep Condition Indicator, mood and anxiety symptoms and psychosocial functioning, such as Edinburgh Postnatal Depression Scale, Mood Disorder Questionnaire, State-Trait Anxiety Inventory, Work and Social Adjustment Scale. At T0, 181 pregnant women were included. Insomnia disorder affected 22.3% at T0, 23.5% at T1 and 16.2% at T2. Women with insomnia disorder at baseline were significantly more affected by concurrent anxiety and depressive symptoms, had higher bipolar diathesis and poorer psychosocial functioning in the perinatal period. Prenatal insomnia disorder predicted anxiety (T0: odds ratio 4.44, p << 0.001; T1: odds ratio 4.009, p = 0.042) and depressive symptoms (T0: odds ratio 2.66, p = 0.015; T1: odds ratio 11.20, p = 0.001; T2: odds ratio 12.50 p = 0.049) in both the prenatal and postnatal period. It also predicted poor psychosocial function during the prenatal (odds ratio 3.55, p = 0.003) and postpartum periods (T1: odds ratio 2.33, p = 0.004). Insomnia disorder is emerging as an important prenatal factor that may contribute to concurrent and postpartum psychopathology.© 2024 European Sleep Research Society.