This study was undertaken to evaluate the correlation between preoperative Serum markers and pelvic adhesions in endometriosis patients and to explore the markers’ clinical value for outcome prediction. Preoperative blood Serum and CA 125 results were obtained and pelvic adhesion scores were calculated. The patient group with adhesion scores less than 28 points was defined as the mild adhesion group, and those with a score of 28 or more were members of the severe adhesion group. The CA 125 level was significantly higher in the severe adhesion group than in the mild adhesion group. The CA 125 level, size of the largest cyst, and WBC count were associated with the level of pelvic adhesion. Adhesion scores were significantly higher in the CA 125 ≥ 35 U/mL group than in the CA 125 < 35 U/mL group. Patients with a preoperative CA 125 level higher than 35 U/mL are at high risk for pelvic adhesion.