Background <p>Syndromic surveillance systems leverage non-diagnostic data sources to enable the early detection of infectious gastroenteritis outbreaks. However, their use in high-income countries (HICs) remains underexplored. This scoping review explores published literature on syndromic surveillance for gastroenteritis outbreaks in HICs, focusing on the types of data used, their effectiveness, and reported outcomes.</p> Methods <p>A systematic search was conducted in PubMed, Embase, Scopus, and CINAHL for studies published from 2000 onwards. This scoping review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. Data extraction was conducted using a structured form adapted from the Joanna Briggs Institute (JBI) guidelines and the Centers for Disease Control and Prevention (CDC) framework for evaluating surveillance systems was used to systematically guide the extraction. Studies using diagnostic data or in-person healthcare visit data (e.g., GP or ED presentations) were excluded, in line with the syndromic surveillance purpose of early detection in HICs.</p> Results <p>Ten studies met the inclusion criteria. The most common data sources were over-the-counter (OTC) medication sales (<i>n</i> = 5) and telehealth consultations (<i>n</i> = 4), followed by web-based queries (<i>n</i> = 2) and school absenteeism reports (<i>n</i> = 1). OTC and telehealth data provided timely, sensitive, and representative outbreak signals. However, challenges (e.g., seasonal stockpiling, demographic variability) affected OTC sales, while shifts in health-seeking behaviour influenced telehealth data reliability. Web-based queries showed early warning potential but were limited by geographic and demographic biases. School absenteeism data were useful for child-focused settings but had reporting limitations.</p> <p>Most studies assessed timeliness and sensitivity, with limited evaluations of other key attributes such as representativeness, acceptability, and stability. No studies explicitly considered health-seeking behaviour as a rationale for data selection.</p> Conclusions <p>This scoping review underscores the potential of syndromic surveillance for detecting gastroenteritis outbreaks in high-income countries. While most data sources could provide a signal for early outbreak detection, the findings highlight the need for more comprehensive evaluations, improved data representativeness, and the integration of health-seeking behaviour considerations in syndromic surveillance system design. These areas should be the focus of future research to enhance the effectiveness of syndromic surveillance for gastroenteritis in high-income countries.</p>