Background: Depression and anxiety symptoms are commonly experienced by women during the perinatal period. Changes in sleep and sleep quality are typical throughout pregnancy and early postpartum. However, little is known about relationships between insomnia symptoms and psychiatric symptoms in perinatal women. The objective of the present study is to characterize the burden of insomnia symptoms in perinatal women seeking outpatient psychiatric treatment and to examine relationships between insomnia and symptoms of depression and anxiety. Methods: Data from 257 pregnant or postpartum women who sought outpatient psychiatric treatment at a university hospital-affiliated clinic were extracted from an existing clinical management database. Data included validated self-report measures assessing insomnia (Insomnia Severity Index [ISI]), mood (Edinburgh Postnatal Depression Scale [EPDS]), and generalized anxiety (Penn State Worry Questionnaire [PSWQ]). Results: Fifty-two percent of women reported symptoms of insomnia, 75% reported symptoms of depression, and 61% reported symptoms of generalized anxiety. After controlling for PSWQ, the partial correlation between EPDS and ISI was 0.15 and 0.37 for pregnant and postpartum women, respectively. After controlling for EPDS, the partial correlation between PSWQ and ISI was 0.20 and 0.12 for pregnant and postpartum women, respectively. Women with clinically significant ISI scores had significantly higher odds for reporting symptoms consistent with depression (odds ratio [OR] 7.7) and generalized anxiety (OR 2.55) compared to women with lower ISI scores. Conclusions: Insomnia symptoms affected a significant proportion of the perinatal women in this sample. These symptoms are linked to symptoms of depression and anxiety in treatment-seeking pregnant and postpartum women. Perinatal women seen in psychiatric treatment settings should be routinely screened for sleep problems.