Background A lifestyle comprising a healthy diet, light alcohol consumption, no smoking, and moderate or intense physical activity has been associated with reduced risk of cardiovascular disease (CVD). We examined the association of a healthy lifestyle index (HLI), derived from scores for each of these components plus waist circumference, with the risk of incident CVD and CVD subtypes in postmenopausal women with normal body mass index (18.5–<25.0 kg/m ² ). Methods and Results We studied 40 118 participants in the Women's Health Initiative, aged 50 to 79 years at enrollment, with a normal body mass index and no history of CVD. The HLI score was categorized into quintiles. We estimated multivariable adjusted hazard ratios (HR) and 95% CIs for the association of HLI with risk of CVD and CVD subtypes using Cox regression models. A total of 3821 cases of incident CVD were ascertained during a median follow‐up of 20.1 years. Compared with the lowest quintile (unhealthiest lifestyle), higher HLI quintiles showed inverse associations with the risk of CVD (HR _quintile−2 =0.74 [95% CI, 0.67–0.81]; HR _quintile−3 =0.66 [95% CI, 0.60–0.72]; HR _quintile−4 =0.57 [95% CI, 0.51–0.63]; and HR _quintile−5 =0.48 [95% CI, 0.43–0.54], P‐trend =<0.001). HLI was also inversely associated with risks of stroke, coronary heart disease, myocardial infarction, angina, and coronary revascularization. Subgroup analyses, stratified by age (≤63 years vs >63 years), body mass index (</≥ 22.0 kg/m ² ), and general health status (absence/presence of hypertension, diabetes, or lipid‐lowering drug use) also showed inverse associations between HLI and risk of CVD. Conclusions Among postmenopausal women with a normal body mass index, adherence to a healthy lifestyle is associated with a reduced risk of clinical CVD and CVD subtypes, underscoring the cardiovascular benefits of maintaining a healthy lifestyle, even for women with a healthy weight.