Objective To explore the impact of the COVID-19 pandemic on pain and fatigue symptoms and their interactions with the impact on mental health in people with endometriosis. Design Global cross-sectional survey. Setting Online survey. Sample A total of 4717 adults with a surgical or radiological diagnosis of endometriosis. Methods An online global study collected data in 5 languages between 11th May to 8th June 2020. The survey included questions on current-status and changes of endometriosis-symptoms, mental health, demographics, and the impact of the COVID-19 pandemic on the respondents’ lives. Main Outcome Measures Self-reported changes to endometriosis-associated symptoms (pelvic pain, tiredness/fatigue, bleeding) and to mental health during the early stages of the COVID-19 pandemic. Results Respondents reported a marked worsening of their endometriosis symptoms (endo-associated pain (39.3%; 95% CI [37.7, 40.5]), tiredness/fatigue (49.9%; 95% CI [48.4, 51.2]) and bleeding (39.6%; 95% CI [38.2, 41])) and mental health (38.6%; 95% CI [37.2, 39.9]). Those with a pre-existing mental health diagnosis (38.8%) were more negatively impacted. The worsening of pain and TF were significantly correlated with worsening of mental health (p<0.001) and these relationships were found to be weakly mediated by pain catastrophising scores (pain: effect size: 0.071, LLCI= 0.060, ULCI= 0.082, TF: effect size: 0.050, LLCI= 0.040, ULCI= 0.060). Conclusions This study demonstrates that stressful experiences impact the physical and mental health of people with endometriosis. The findings highlight the need to consider psychological approaches in the holistic management of people with endometriosis.