The American College of Physicians (ACP) recently identified cognitive behavioral therapy for insomnia (CBT-I) as the first-line treatment for insomnia. Although CBT-I improves sleep outcomes and reduces the risks associated with reliance on hypnotics, patients are rarely referred to this treatment, especially in primary care where most insomnia treatment is provided. We reviewed the evidence about barriers to CBT-I referrals and efforts to increase the use of CBT-I services. PubMed, PsycINFO, and Embase were searched on January 11, 2018; additional titles were added based on a review of bibliographies and expert opinion and 51 articles were included in the results of this narrative review. Implementation research testing specific interventions to increase routine and sustained use of CBT-I was lacking. Most research focused on pre-implementation work that revealed the complexity of delivering CBT-I in routine healthcare settings due to three distinct categories of barriers. First, system barriers result in limited access to CBT-I and behavioral sleep medicine (BSM) providers. Second, primary care providers are not adequately screening for sleep issues and referring appropriately due to a lack of knowledge, treatment beliefs, and a lack of motivation to assess and treat insomnia. Finally, patient barriers, including a lack of knowledge, treatment beliefs, and limited access, prevent patients from engaging in CBT-I. These findings are organized using a conceptual model to represent the many challenges inherent in providing guideline-concordant insomnia care. We conclude with an agenda for future implementation research to systematically address these challenges.