Abstract Aims Body mass index (BMI) defined obesity is paradoxically associated with lower all-cause mortality in patients with known cardiovascular disease. This study aims to determine the role of physical fitness in the obesity paradox in women with ischaemic heart disease (IHD). Methods and Results Women undergoing invasive coronary angiography with signs/symptoms of IHD in the Women’s Ischemia Syndrome Evaluation (WISE) prospective cohort (enrolled 1997–2001) were analysed. This study investigated the longer-term risk of major adverse cardiovascular events (MACE) and all-cause mortality associated with BMI and physical fitness measured by Duke Activity Status Index (DASI). Overweight was defined as BMl ≥25 to 30 kg/m2, obese as BMI ≥30 kg/m2, unfit as DASI scores <25, equivalent to ≤7 metabolic equivalents. Among 899 women, 18.6% were normal BMI-fit, 11.4% overweight-fit, 10.4% obese-fit, 15.3% normal BMI-unfit, 23.8% overweight-unfit, and 30.4% obese-unfit. In adjusted models compared to normal BMI-fit, normal BMI-unfit women had higher MACE risk [hazard ratio (HR) 1.65, 95% confidence interval (CI) 1.17–2.32; P = 0.004]; whereas obese-fit and overweight-fit women had lower risk of mortality (HR 0.60, 95% CI 0.40–0.89; P = 0.012 and HR 0.62, 95% CI 0.41–0.92; P = 0.018, respectively). Conclusion To address the paradox of body weight and outcomes in women, we report for the first time that among women with signs/symptoms of IHD overweight-fit and obese-fit were at lower risk of long-term all-cause mortality; whereas normal BMI-unfit were at higher risk of MACE. Physical fitness may contribute to the obesity paradox in women, warranting future studies to better understand associations between body weight, body composition, and physical fitness to improve cardiovascular outcomes in women.