Background <p>Lead (Pb) exposure is a global health concern, with recognized adverse effects on skeletal health. However, its relationship with body composition across menopausal stages remains unclear. This study aimed to examine the associations between blood lead levels (BLL) and key body composition parameters—lumbar bone mineral density (BMD), appendicular lean mass index (ALMI), and appendicular fat mass index (AFMI)—in middle-aged women.</p> Methods <p>In this cross-sectional study, we analysed data from 1,522 women aged 40–59 years who participated in the National Health and Nutrition Examination Survey (NHANES) 2011–2018. We employed weighted multivariable linear regression models to examine the associations between log-transformed BLL (LnBLL) and body composition parameters, adjusting for potential confounders.</p> Results <p>Postmenopausal women exhibited significantly higher BLL compared to premenopausal women, along with lower lumbar BMD and ALMI. LnBLL was significantly and inversely associated with lumbar BMD (β = -0.02; 95% CI: -0.03 to -0.01), ALMI (β = -0.39; 95% CI: -0.49 to -0.29), and AFMI (β = -0.61; 95% CI: -0.78 to -0.45). Subgroup analyses revealed that the inverse association between LnBLL and lumbar BMD was statistically significant in premenopausal women (β = -0.03; 95% CI: -0.05 to -0.01), but not in postmenopausal women (β = -0.01; 95% CI: -0.03 to 0.01). In contrast, LnBLL exhibited stronger inverse associations with both ALMI and AFMI among postmenopausal women (ALMI: β = -0.46; 95% CI: -0.60 to -0.32; AFMI: β = -0.65; 95% CI: -0.87 to -0.43).</p> Conclusions <p>Our findings show complex, menopause-dependent relationships between BLL and body composition parameters in middle-aged women. These results highlight the critical importance of considering menopausal status in future Pb toxicity studies.</p>