Endometriosis is a chronic disorder, clinically associated with chronic pelvic pain, dyspareunia, dysmenorrhea, and infertility. Its socio-economic impact is extensive, given the large number of affected women in reproductive age, its symptomatology (that interferes with normal social life and the patient's ability to work), and its frequent association with infertility. Nonetheless, the diagnosis of endometriosis is still difficult and late in the evolution of the disorder. The authors have used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) criteria to make a systematic review of the literature of the last 28 years, seeking to identify potential biomarkers useful for a non-invasive diagnosis of endometriosis. The authors have highlighted more than 50 biomarkers in the studies included in the present report, but they have not succeeded in identifying a clinically useful non-invasive diagnostic biomarker or panel of biomarkers. More studies are needed before biomarkers can be introduced in clinical practice.