The primary aim of this research is to investigate the predictive value of subdural effusion thickness in determining the progression of post-traumatic subdural effusion to chronic subdural hematoma. Studying this progression is crucial as it helps in early diagnosis and effective management of chronic subdural hematoma, which is a serious and life-threatening condition. This research is valuable and relevant for improving patient outcomes and reducing the associated risks and complications.We conducted a retrospective examination of the clinical data obtained from 124 patients who were treated for post-traumatic subdural effusion at our neurosurgery department between March 2017 and March 2021. The data collection process involved reviewing the patients' medical records, radiographic images, and follow-up visits. We used strict criteria for patient selection, including a confirmed diagnosis of post-traumatic subdural effusion, availability of follow-up data, and no prior history of chronic subdural hematoma. Patients who experienced a progression of subdural effusion to chronic subdural hematoma were assigned to the hematoma group (26 cases). In comparison, those who did not show such progression were categorized into the effusion group (98 cases). We endeavored to identify potential risk factors contributing to the progression from subdural effusion to chronic subdural hematoma. The predictive strengths of these risk factors were evaluated using receiver operating characteristic (ROC) curves.There were no statistically significant disparities between the two groups in terms of gender, hypertension, COPD, and GCS scores (P > .05). However, significant differences were noted in the variables of age, tSAH, the location of subdural effusion, and subdural effusion thickness (P < .05). Multivariate logistic regression analysis disclosed age (1.213), tSAH (12.542), and subdural effusion thickness (1.786) as independent risk factors for the conversion of TSE to CSDH (P < .05). The ROC curve showed the AUC values of age, tSAH, and subdural effusion thickness for predicting CSDH to be 0.739, 0.670, and 0.820, respectively, with a combined AUC value of 0.942, thereby outperforming the individual tests.In patients suffering from post-traumatic subdural effusion, the thickness of the subdural effusion emerges as a strong predictor for its progression into a chronic subdural hematoma. Clinicians should be particularly cautious when the effusion thickness exceeds 10.7 mm, as the likelihood of transformation increases significantly. These findings have important implications for clinical practice and patient management, highlighting the need for prompt and effective treatment to prevent chronic complications.