©2020 Chang, Baker, Dos Santos Marques, et al. BACKGROUND: Low health literacy is associated with poor health outcomes in many chronic diseases and may have an important role in determining surgical outcomes. This study aims to comprehensively review the current state of science on adult health literacy in surgery and to identify knowledge gaps for future research. METHODS: Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic search was conducted to identify all studies from January 2002 through May 2018 that used validated instruments to assess health literacy among adult patients undergoing surgery. Studies were assessed for quality using the Newcastle-Ottawa scale and evaluated on findings by their focus on identifying health literacy levels, understanding associations with surgical outcomes, and/or developing interventions to address low health literacy. KEY RESULTS: There were 51 studies on health literacy with data from 22,139 patients included in this review. Low health literacy was present in more than one-third of surgical patients (34%, interquartile range 16%-50%). The most commonly used validated instrument for assessment of health literacy in the surgical population was the Newest Vital Sign. Most studies were focused on identifying the prevalence of low health literacy within a surgery population (84%, n = 43). Few studies focused on understanding the association of health literacy to surgical outcomes (12%, n = 6) and even fewer studies developed interventions to address health literacy (4%, n = 2). DISCUSSION: Low health literacy is common among surgical patients. Important opportunities exist to better understand the role of health literacy in determining surgical outcomes and to develop more health literacy-sensitive models of surgical care. [HLRP: Health Literacy Research and Practice. 2020;4(1):e45-e65.] PLAIN LANGUAGE SUMMARY: Health literacy has not been well-studied in surgery but likely plays an important role. In this article, we reviewed all current research on health literacy in surgery to help us understand where we are at and where we need to go. We found that low health literacy is common and we need more ways to address it in surgery.