Objective: Chest pain is one of the most frequent causes for presentation to emergency departments (EDs). The majority of patients will undergo diagnostic workup including stress testing to rule out an acute coronary syndrome, but very few patients will be diagnosed with a cardiac cause for their pain. Patients under 40 years represent a lower risk group in which routine stress testing may be of little benefit. This systematic review sought to determine the diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years. Methods: Electronic databases were searched for relevant studies. The quality of the included primary studies was assessed using the National Health and Medical Research Council evidence hierarchy and the McMaster Critical Appraisal Tool for Quantitative Studies. Descriptive statistics summarized the findings. Results: Five primary studies were included in the review (all level III-3 evidence); 7 additional sources of relevant data were also included. Diagnostic yield of routine stress testing in low- and intermediate-risk patients under 40 years is reported between 0% and 1.1%. Combined data from included primary studies demonstrated just 4 out of 1683 true positive stress tests (0.24%), only one of which was definitively confirmed by coronary angiogram; additional data sources identified just 1 out of 310 true positive stress tests (0.32%). Conclusions: Diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years is low. However, better quality studies are required to be able to draw definitive conclusions.