Sleep disturbance, particularly insomnia, is prevalent in cancer patients undergoing chemotherapy. Our preliminary data show that our novel intervention, Brief Behavioral Therapy for Insomnia (BBT-I), significantly reduces insomnia in breast cancer patients receiving chemotherapy. BBT-I is modeled on standard cognitive behavioral therapy for insomnia (CBT-I), including both stimulus control and sleep scheduling, and has been successfully modified to make it more suitable for breast cancer patients undergoing adjuvant or neoadjuvant chemotherapy with recently developed insomnia symptoms. Our preliminary research suggests that BBT-I is an acceptable and feasible intervention for insomnia in breast cancer patients that might also lead to improvement in fatigue and cognitive difficulties. Methods: This research is designed to determine the efficacy of the BBT-I in comparison with the attention-matched behavioral control in reducing insomnia, fatigue, and cognitive difficulties in breast cancer patients. In addition, this study will examine the potential involvement of moderators (age, depression, anxiety, and hot flashes), specific behavioral mechanisms (maladaptive sleep behaviors, dysfunctional beliefs and attitudes), and physiological mechanisms (dysregulated circadian rhythms, disrupted wake-sleep cycles, and autonomic tone) as potential mediators of intervention-related changes in insomnia and the secondary outcomes of fatigue and cognitive difficulties. To address these aims, 180 breast cancer patients with acute insomnia during chemotherapy treatment will be recruited and randomized to receive either BBT-I or a behavioral control focused on Healthy Eating Education. Each intervention condition will consist of 2 face-to-face sessions + 4 phone calls, delivered over a period of six weeks. Assessments will include sleep diary, questionnaires, neuropsychological testing, actigraphy, heart rate variability measurement, and salivary cortisol collection at baseline, post-intervention, and 6- and 12 months follow ups. By offering this intervention during chemotherapy when patients are just beginning to develop insomnia, we hope to alleviate and avoid the development of chronic insomnia in the survivorship phase.