Cognitive behavioral therapy (CBT) is one of the most effective psychotherapies for the treatment of depression, insomnia, and their comorbidity. CBT targets maladaptive cognitions and behaviors to reduce emotional distress and subsequently achieve its intended outcomes, such as symptom reduction in depression and improved sleep in insomnia. This chapter details the origins of the cognitive behavioral model, specific treatment components included in CBT for depression (CBT-D) and CBT for insomnia (CBT-I), a summary of the research evidence for CBT-D and CBT-I, and clinical case vignettes for each of these treatments. This chapter also discusses technological innovations in CBT-D and CBT-I, similarities and differences between these two treatments, recommendations for treating comorbid depression and insomnia, diversity considerations when applying these treatments to clients, and finally, clinical recommendations for practitioners.