Objective To investigate the sleep quality, mindful attentional awareness level and exercise endurance in patients with coronary artery disease after percutaneous coronary intervention (PCI), and to explore the mediating effect of mindful attention awareness level between sleep quality and exercise endurance. Methods Convenience sampling method was used to select 93 post-PCI patients who underwent cardiopulmonary exercise test (CPET) in Department of Cardiovasology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from Aug. 2020 to Jul. 2021. The general information questionnaire, mindful attention awareness scale (MAAS) and Pittsburgh sleep quality index scale (PSQI) were used to investigate the patients' general condition, the level of mindful attention awareness and sleep quality of the patients. The maximal oxygen uptake (VO_{2 max}) from the results of the CPET was used to assess the patients' exercise endurance. Results Totally 89 valid questionnaires were collected. The MAAS score of the 89 patients was 65.00 (60.50, 70.50), the PSQI score was 8.00 (6.00, 9.00), and the VO_{2 max} was (1 203.29±368.12) mL/min. The PSQI score was negatively correlated with the VO_{2 max} (r_s=-0.482, P<0.01), the MAAS score was negatively correlated with the PSQI score (r_s=-0.402, P<0.01), and the MAAS score was positively correlated with the VO_{2 max} (r_s=0.454, P<0.01); among them, female patients or ones with previous myocardial infarction showed higher correlation among the 3 variables (|r_s|>0.5, P<0.01). The results of the mediation effect analysis showed that the level of mindfulness had a partial mediation effect between sleep quality and exercise endurance in patients with coronary heart disease after PCI (the mediation effect value was -23.802, 95% confidence interval -46.461- -7.277), and the mediation effect accounted for 25.29% of the total effect. Conclusion Sleep quality has a predictive effect on exercise endurance in patients with coronary artery disease after PCI, and the level of mindful attention awareness plays a mediation role between sleep quality and exercise endurance.