["Journal of Traumatic Stress, EarlyView. ", "\nAbstract\nThis study aimed to conduct the first psychometric evaluation of both the full 33‐item and short‐form nine‐item versions of the Posttraumatic Cognitions Inventory (PTCI and PTCI‐9, respectively) in a sample of first responders from China. A total of 1,448 male first responders completed the PTCI, Life Events Checklist for DSM‐5 (LEC‐5), and PTSD Checklist for DSM‐5 (PCL‐5). Confirmatory factor analysis (CFA), measurement invariance, internal consistency, and criterion validity were used to examine the validity and reliability of the PTCI and PTCI‐9. Optimal cutoff scores were determined via receiver operating characteristic (ROC) curve analysis. CFA results indicated inadequate fit for the original three‐factor and alternative four‐factor models of the PTCI, whereas the PTCI‐9 demonstrated good model fit, root mean square error of approximation (RMSEA) = .052, confirmatory fit index (CFI) = .96, Tucker–Lewis index (TLI) = .93, goodness of fit index (GFI) = .98. The PTCI‐9 showed measurement invariance across subgroups with and without interpersonal trauma exposure. Both versions of the measure were significantly related to PCL‐5 scores, with no difference in correlation strength. Both versions showed good internal consistency, PTCI: ω = .98, PTCI‐9: ω = .90. ROC analyses suggested optimal cutoff scores of 53 for the PTCI and 16 for the PTCI‐9. These results indicate that the PTCI‐9 demonstrates comparable or superior psychometric properties to the full PTCI among first responders, showing greater practical utility due to its brevity.\n"]