Enoxaparin is a low molecular weight heparin that is principally prescribed for the treatment and prevention of thromboembolic disorders. In clinical practice, the abdominal site for subcutaneous enoxaparin administration is most preferable because of its simplicity and safety. However, subcutaneous enoxaparin bioavailability in critically ill patients with ascites is uncertain. According to this case report, the bioavailability and absorption of subcutaneous enoxaparin was potentially impaired in a critically ill patient with ascites and local edema based on the therapeutic drug monitoring of anti-factor Xa levels.