Objective: To analyze the reliability and validity of the Johns Hopkins Fall Risk Assessment Scale (JHFRAS) for out-of-bed fall risk in patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI). Methods: This study adopted continuity inclusion with the Chinese version of JHFRAS to test patients with AMI after PCI who were admitted to our hospital from January 2021 to December 2022. The occurrence of falls during out-of-bed activities was counted through follow-up, and the predictive value of the scale was assessed by using the area under the curve (AUC) of the receiver operator characteristic curve and determining sensitivity, specificity, Jordon's index, and critical value. The internal consistency reliability (Cronbach's α coefficient), interrater reliability (Spearman correlation analysis was conducted to analyze the scores obtained through the independent and simultaneous assessment of two reviewers who were unaware of the content and results of the scale), content validity (expert evaluation involving four experts), and criterion-related validity (the score of the Morse fall assessment scale [rMFS] was used as an indicator of criterion-related validity) were determined. Results: Through follow-up, this study found that 11 cases experienced falls during out-of-bed activities and 69 cases did not experience falls. The JHFRAS scores of the nonfall and fall groups were significantly different (p < 0.05). JHFRAS, which was designed to predict the risk of falls during out-of-bed activities in post-PCI patients with AMI, had an AUC of 0.880, a sensitivity of 0.937, a specificity of 0.824, a Jordon's index of 0.760, and a critical value of 9 points. Its Cronbach's α coefficient was 0.803. The assessment data from two reviewers were analyzed via intragroup coefficient analysis and yielded a Spearman's rank correlation coefficient of 0.948. The overall content validity of the scale was 0.968. The content validity indices of age, fall history, urine and defecation excretion amount, high-risk drug use, stent number, action capability, and cognitive ability were 0.915, 0.924, 0.938, 0.920, 0.954, 0.960 and 0.972, respectively. All correlation coefficients were significant at the 0.01 level. The scores of each dimension of rMFS and JHFRAS showed positive correlations. Conclusions: JHFRAS has good reliability and validity and can be used to assess the fall risk of out-of-bed activities in patients with AMI after PCI.