Background/Objectives: Prior studies linked higher blood phytoestrogen (phytoE) levels of daidzein to beneficial lipoprotein profiles, and higher genistein levels related to worse coronary microvascular dysfunction in women with suspected ischemic heart disease (IHD). However, relationships to adverse outcomes remain unclear. We investigated the associations between eight serum phytoE and major adverse cardiac events (MACE) including myocardial infarction, stroke, hospitalization for heart failure and angina, cardiovascular and all-cause mortality, in women undergoing functional coronary angiography (FCA) for suspected ischemia. Subjects/Methods: We evaluated 143 women enrolled in the Women’s Ischemia Syndrome Evaluation (1996–2001) for serum phytoE levels and 10-year outcomes. Median follow-up duration was 6.08 years (range 0.01–8.16) for time to MACE and 9.11 years (range 0.01–11.08 years) for time to death. Kaplan–Meier plots were analyzed and Cox regression models adjusted for age, body mass index, hypertension, diabetes, dyslipidemia and tobacco use. Results: The median age was 54.7 (range 20.6–76.1) years and BMI was 29.3 (range 18.4–57.2). Of the cohort, 80.4% had nonobstructive coronary artery disease, 56% had hypertension, 22.4% had diabetes, 58.1% had dyslipidemia and 59.4% of the women used tobacco. Each unit decrease in log glycitin was associated with increased MACE hazard (HR 1.97, 95% [CI 1.23, 3.14], p = 0.005). Glycitin absence was associated with earlier angina hospitalization (log rank p = 0.05). After 6 years, MACE increased with each unit decrease in log genistein (HR 6.17, 95% [CI 1.81, 20.8], p = 0.0036). Other phytoE did not show statistically significant associations with outcomes. Conclusions: Among women with suspected IHD undergoing clinically indicated invasive FCA, low serum glycitin was associated with increased MACE and earlier angina hospitalization, while low genistein was associated with increased MACE after 6 years. Future studies are needed regarding phytoE, nutrition, outcomes and possibly supplementation.