Background: Acute appendicitis is the acute inflammation of appendix accounting to 7-10% of acute abdomen cases. The complications vary from surgical site infection to enterocutaneous fistula and stump appendicitis. The surgical site infections after appendicectomy are postoperative nosocomial infections affecting the incision site, deeper tissues and organs at the operative site within 30 days of surgery. The study was aimed at predicting subcutaneous fat thickness causing surgical site infection in open appendicectomy wounds. Methods: This prospective study was conducted in Trichy SRM Medical College Hospital and Research Centre, Tamil Nadu from January to June 2021 in 82 patients. Patients who underwent open appendicectomy for uncomplicated acute appendicitis were included. Patients underwent preoperative Ultrasound abdomen to measure the subcutaneous fat thickness in right iliac fossa and was correlated with post operative surgical site infection for 1 month. The subcutaneous fat thickness was divided into three groups; I- 5.5 mm and below, II- 5.5 to 7.5 mm and III- more than 7.5 mm. Results: The results show that there was an increased association of surgical site infection in patients with increased subcutaneous fat thickness at incision site with mean of 6.25 and SD of 1.49. Conclusions: The study showed that subcutaneous fat thickness is a predictor for development of surgical site infection in open appendicectomy wounds. The subcutaneous fat thickness association in causing surgical site infection in open appendicectomy wounds is of linear association.