Background and Objectives: It is widely recognized that sarcopenia increases postoperative complications in trauma patients. However, the effects on prognosis remain unclear. This study aimed to evaluate the impact of sarcopenia on 90-day readmission and overall survival (OS) in abdominal trauma patients. Methods and Study Design: 485 consecutive patients who underwent abdominal surgery after trauma in our institution were enrolled. Sarcopenia was diagnosed with low muscle mass and low muscle strength-handgrip. Multivariate logistic regression analysis was performed to identify factors that contributed to 90-day readmission and OS. Cox logistic regression analysis was used to assess the relationship between sarcopenia and OS. Results: Sarcopenia was present in 120 of 485 patients (24.7%) with abdominal trauma within one week after admission based on the diagnostic cut-off values (40.9 cm^2/m^2 for men and 36.8 cm^2/m^2 for women). 90-day readmission was significantly higher in the sarcopenia group (p=0.019), and OS lower in the sarcopenia group (p=0.025). Sarcopenia was an independent predictor of 90-day readmission [odds ratio (OR): 5.34, 95% confidence interval (CI): 2.52-11.3]. Conclusions: Sarcopenia was associated with high 90-day readmission and low OS in abdominal trauma patients, and it was an independent risk factor for 90-day readmission.