Although patient–provider language concordance has the potential to reduce health disparities for people with limited English proficiency, no previous work has synthesized this literature. Our systematic review sought to describe the characteristics of studies examining relationships between language concordance and health outcomes, summarize the nature of observed associations, and propose an evidence map and research agenda. A comprehensive search of published articles identified 38 quantitative studies for inclusion. Most studies were cross-sectional, conducted in primary care, concentrated in Western states, and focused on Spanish speakers and physician providers. Results were split between supporting a positive association versus no association of language concordance with patient behaviors, provider behaviors, interpersonal processes of care, and clinical outcomes. Several methodological limitations were identified. Based on these results, we developed an evidence map, identified knowledge gaps, and proposed a research agenda. There is a particular need for quasi-experimental longitudinal studies with well-characterized samples.