Endometriosis, affecting around 176 million women globally, is typically diagnosed through invasive laparoscopic inspection and histological confirmation. Due to the invasiveness of this method, noninvasive diagnostic alternatives like serum CA-125 assays are gaining interest. This study aims to determine the correlation between the tumor marker CA-125 and the stages of endometriosis, as classified by the revised American Society for Reproductive Medicine (rASRM) score. Data were retrospectively collected from the medical records of 24 reproductive-age women diagnosed with endometriosis at Dr. Moewardi General Hospital in Surakarta City, Indonesia. The dataset included patient age, serum CA-125 levels, rASRM scores, comorbidities, and surgical history. Statistical analysis involved the use of Pearson Chi-Square tests for nominal variables and independent t-tests or Mann-Whitney U-tests for scaled variables to evaluate the association between endometriosis stages (grouped into Stage I-II and Stage III-IV) and CA-125 levels (categorized as normal or elevated). A significant correlation was observed between higher stages of endometriosis (stage III-IV) and elevated CA-125 levels (p=0.040). Additionally, normal CA-125 levels were significantly associated with lower stages of endometriosis (stage I-II) (p=0.046). Furthermore, an association was found between type 2 diabetes and elevated CA-125 levels (p=0.037). In conclusion, our study suggests that elevated CA-125 levels correlate with higher stages of endometriosis (stage III-IV) and type 2 diabetes, indicating its potential as a biomarker for endometriosis severity.