Insomnia and disturbed sleep are common during pregnancy. This study investigated the effectiveness of group cognitive-behavioral therapy for insomnia (CBT-I) delivered in pregnancy. Thirteen pregnant women with insomnia participated in five weekly CBT-I group sessions. All participants completed the study and provided baseline and follow-up data. Significant reductions in insomnia symptoms and increases in subjective sleep quality were observed over the course of the study. Diary and actigraphy assessments of sleep also changed, such that participants reported less time in bed (TIB), shorter sleep onset latency (SOL), increased sleep efficiency (SE), and increased subjective total sleep time (TST). Additionally, symptoms of depression, pregnancy-specific anxiety, and fatigue all decreased over the course of treatment. Effect sizes ranged from medium to large. CBT-I delivered during pregnancy was associated with significant improvements in sleep and mood. The next step in this area of inquiry is to better establish effectiveness via a randomized controlled trial.