The objectives of this review were (1) to examine characteristics associated with enrollment and utilization of portals among patients with diabetes and (2) to identify barriers and facilitators of electronic patient portal enrollment and utilization. PubMed and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) were systematically searched for papers reporting original research using quantitative or qualitative methods on characteristics, barriers, and facilitators associated with portal enrollment and utilization among patients with diabetes in the United States. The search was limited to articles published between February 1, 2005 (the date of the national symposium on personal health records) and January 1, 2014. Sixteen articles were identified. Of these, nine were quantitative, three were qualitative, and four used mixed-methods. Several demographic characteristics, having better-controlled diabetes, and providers who engaged in and encouraged portal use were associated with increased portal enrollment and utilization. Barriers to portal enrollment included a lack of patient (1) capacity, (2) desire, and (3) awareness of portal/portal functions. Barriers to portal utilization included (1) patient capacity, (2) lack of provider and patient buy-in to portal benefits, and (3) negative patient experiences using portals. Facilitators of portal enrollment and utilization were providers and family members recommending and engaging in portal use. Improved usability, increased access, educating patients how to use and benefit from portals, and greater endorsement by providers and family members might increase portal enrollment and utilization. As more providers and hospitals offer portals, addressing barriers and leveraging facilitators may help patients with diabetes achieve potential benefits.