This study was performed to investigate the effect of early pressure dressing on the prevention of postoperative subdural effusion secondary to decompressive craniectomy (DC) in patients with severe traumatic brain injury (STBI). Patients with STBI who had undergone DC for refractory increased intracranial pressure between January 2008 and December 2011 (n = 169) were randomly divided into early pressure dressing (n = 82) and control (n = 87) groups. Early pressure dressing with an elastic bandage or general wrapping (control treatment) was applied 7 to 10 days after DC. Patients' age, sex, preoperative Glasgow Coma Scale score, incidence rate of subdural effusion, hospitalization time, and postoperative Glasgow Outcome Scale score were compared between groups. Intracranial pressure was measured immediately before and on the day after pressure dressing. No significant difference in age, sex, preoperative Glasgow Coma Scale score, or postoperative Glasgow Outcome Scale score was observed between groups (P > 0.05). Subdural effusion incidence rates were significantly lower in the early pressure dressing group than those in the control group (χ² = 5.449, P = 0.021), and a larger proportion of patients in the early pressure dressing group was hospitalized for 30 days or less (χ² = 5.245, P = 0.027). Early pressure dressing 7 to 10 days after DC, which is a noninvasive, simple procedure, reduced the incidence rate of subdural effusion and shortened hospitalization time after DC for STBI.