Although the Impact Event Scale-Revised is widely used, its factor structure is still controversial. In addition, its longitudinal measurement invariance (LMI) remains uninvestigated. In this sense, we carried out three studies to investigate its psychometric properties. In Study 1, we evaluated the factorial structure of the scale comparing the different models existing in the literature in Brazilian samples who responded to the instrument during the COVID-19 pandemic. In Study 2, we provide support for a five-factor model throughout convergent validity with psychological distress and sleep problems, and criterion validity between people with diagnostic of mental disorders. Finally, we evaluated the LMI over a 6-month interval. The results indicated that the five-factor model has excellent goodness of fit and holds strict longitudinal invariance. Additionally, internal consistency and stability coefficients indicate that the scale is appropriate to measure posttraumatic stress symptomatology) in nonclinical samples across multiple assessments. (PsycInfo Database Record (c) 2022 APA, all rights reserved).