Endometriosis has critical implications for women’s quality of life. However, an overview of the current knowledge of this issue is limited. The objective of this systematic review was to determine the extent of endometriosis and its treatment upon women’s health-related quality of life (HRQoL). PubMed, Embase, PsycoINFO, CINAHL and the Cochrane Clinical Trials were searched up to May 2012, and only studies using standardized instruments to evaluate HRQoL in women with endometriosis were selected. Our electronic searches identified 591 citations, of which 39 studies satisfied the inclusion criteria including nine qualitative studies and 30 treatment-related studies. Findings showed that endometriosis impaired women’s HRQoL. Pain was strongly related to a poor HRQoL, and medical or surgical treatment could partially restore this impairment. No conclusive evidence was available on whether endometriosis imposed an additional impairment in HRQoL per se, apart from the decrease caused by chronic pelvic pain, or on the superiority of various hormonal suppression agents. The impacts of disease extent, duration and fertility status upon HRQoL were inconsistent. In summary, HRQoL was impaired in women with endometriosis, and medical or surgical treatment to alleviate pain could partially restore this impairment.