Objective: To investigate the impact of vaping and smoking on ovarian reserve markers anti-Müllerian hormone (AMH) and follicle-stimulating hormone (FSH). Design: Retrospective observational study. Setting: Users of a private at-home testing service. Population: 21,102 women aged 21-45 not taking hormonal contraception with no preexisting common reproductive health conditions. Methods: Serum AMH and FSH was assayed via finger prick samples and medical history data was collected online. The relationship between vaping or smoking, and log-transformed AMH or FSH was assessed via adjusted multiple linear regression. Logistic regression was used to produce odds ratios for age-dependent low AMH. Main Outcome Measures: Serum AMH (pmol/L), FSH (IU/L) and age-dependent low AMH. Results: Current and occasional vaping significantly decreased AMH by 7.76% (95 CI 12.24-3.05%,p=0.002) and 4.88% (95% CI 8.7-0.9%,p=0.017) respectively. Current vaping increased the odds of low AMH by 1.58 (aOR=1.58,95% CI=1.25-1.99,p<0.001) times, however, FSH was unaffected. Current smoking significantly decreased AMH by 10.1% (95 CI 16.13-7.3%,p=0.002), increasing the odds of low AMH by 1.59 (aOR=1.59,95% CI=1.17-2.12,p=0.002) and significantly increasing FSH by 7.4% (95% CI 4.2-10.63%,p<0.001). Conclusions: Both vaping and smoking have negative impacts on ovarian reserve markers. Funding: This work was supported by Hertility Health Ltd. Keywords: Vaping, e-cigarette, smoking, ovarian reserve, anti-müllerian hormone, follicle stimulating hormone