Background: Metabolic syndrome prevalence in cardiac rehabilitation (CR) is high and participants have poor baseline and overall improvement in exercise capacity; however, it is unclear if this is due to participant or CR programlevel factors. The purpose of this research was to describe, in CR participants, the association between metabolic syndrome and change in exercise capacity, and to examine exercise capacity variation by CR program. Methods: Data was abstracted from medical charts in four CR programs. A three-category exposure variable was defined as BMI<27 (reference group) and no metabolic syndrome (n=73), BMI ≥ 27 without metabolic syndrome (n=21), and metabolic syndrome (n=156). Hierarchical linear models examined the association between metabolic syndrome and the rate of change in exercise capacity and variation in exercise capacity by CR program. Results: Sixty-two percent of participants had metabolic syndrome. In multivariable analyses, participants with BMI ≥ 27 without metabolic syndrome and those with metabolic syndrome had slower rates of change in exercise capacity compared to the reference group (β= -0.20, 95% confidence interval (CI): -0.29,-0.10; and β= -0.28, CI: -0.34,- 0.23, respectively). There was no difference between the BMI ≥ 27 without metabolic syndrome and the metabolic syndrome groups. Twenty-seven percent of the difference in exercise capacity was due to CR program. Conclusions: Participants with metabolic syndrome had slower rates of improvement in exercise capacity compared to those without metabolic syndrome. Variation between CR programs highlights the need for standard management of all CR participants but especially for those with metabolic syndrome.