Objective. The aim of this study was to investigate whether platelet indices-mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit (PCT) would be useful as noninvasive biomarkers for determining the severity of endometriosis. Methods. A retrospective review of the medical charts of 164 patients diagnosed with endometriosis and who were operated on between 2001 and 2013 was performed. The stage of endometriosis was determined according to revised American Society for Reproductive Medicine criteria. Results. In patients with advanced endometriosis (Stages 3-4), PLT, PCT levels were found to be significantly higher and MPV, PDW values to be significantly lower when compared to initial endometriosis (Stages 1-2). In addition, there was a significant positive correlation between PLT (r: 0.800, P: 0.001) and PCT (r: 0.727, P: 0.002) and the inflammatory marker white blood cell count (WBC). Conclusion. Our finding may not sufficient for employing platelet indices solely in this differential diagnosis, but our finding could provide a suggestion for clinical physicians so that attention is paid to the value of platelet indices and that these may be taken into account when making decisions about the initial or advanced stages of endometriosis.