Introduction: Inactive lifestyle is associated with decreased cardiorespiratory function and increased chronic non-communicable diseases and death. The aim of this study was to investigate the effect of six weeks of concurrent training (endurance-resistance) on the performance of the cardio-respiratory system in inactive young women. Method: In this quasi-experimental study, 16 inactive women of Tehran city were selected in a targeted and available manner and were randomly placed in two control groups (n = 8) and concurrent exercise (endurance and resistance) (n = 8). After the pre-test (anthropometric tests and gas analyzer), the concurrent exercise group (endurance and resistance) performed the concurrent exercise program for six weeks and three sessions every week, and the subjects of the control group did not have any special exercise. After the six-week training period, measuring anthropometric indices (body mass index (BMI), body fat percentage (PBF), muscle mass (SMM) and hip-to-waist ratio (WHR) and cardiorespiratory indices including (the first ventilatory threshold (VE/VO2), Second ventilatory threshold (VE/VCO2), maximum oxygen consumption (VO2max), respiratory exchange ratio (RER), heart rate (HR), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), expiratory volume forced in one second to forced capacity (FEV1/FVC) and the ratio of oxygen consumption to heart rate (VO2/HR) was done using in-body device and gas analyzer. The data were analyzed by covariance analysis test at the P<0.05. Results: The results showed that six weeks of concurrent training (endurance-resistance) had no significant effect on the values ​​of VO2max, FEV1, FVC, VE/VO2, VE/VCO2, FEV1/FVC, VO2/HR,HR in inactive young women (P<0.05). Also, after the training period, there was no difference in BMI, PBF, SMM and WHR indices between the training and control groups (P<0.05). Conclusion: According to the results of the research, it seems that six weeks of concurrent training (endurance-resistance) does not affect the performance of the cardio-respiratory system in inactive young women.