Background: This exploratory study sought to establish the relationship between endometriosis-related pelvic pain, endometriosis symptom-frequency, and women's subjective wellbeing (SWB). Methods: A purposive sample (N = 2061) of women with endometriosis aged between 18 and 62 years (M = 30.49 ± 7.45) completed an online questionnaire containing a measure of pelvic pain (Biberoglu & Behrman Scale; B&B), endometriosis symptom frequency, and an established measure of SWB (Personal Wellbeing Index: PWI). Results: Mean SWB total scores (58.35 ± 17.90) were considerably lower than those of women in the general population (western normative range = 70-80; mean = 76). On average, women reported moderate levels of pelvic pain (B&B mean = 5.96 ± 1.84), with a mean of 10.87 (± 4.81) endometriosis-related symptoms across the sample. Significant relationships were found between pelvic pain and SWB dimension and total scores (r's = - 0.20 to - 0.43, all p's <.001), and significant small to medium associations between symptom frequency and all but one of the dimensions of SWB (r's = - 0.12 to - 0.23, all p's <.007). In multivariate regression models accounting for age and delay in diagnosis, higher levels of pelvic pain were significantly associated with lower SWB scores across all eight dimensions of the PWI and total score (all p's <.002). Greater symptom frequency was significantly associated with lower levels of SWB for the dimensions of health, future security, life as a whole, and total scores (all p's <.002). Conclusions: SWB was lower in women with endometriosis than SWB in women from the general population, and endometriosis related symptoms and pelvic pain explain significant proportions of the unique variance in women's SWB scores. Psychosocial support is needed for women dealing with endometriosis-related symptoms and pain in order to improve their wellbeing and quality of life.