Introduction <p>The prevalence of osteoporosis (OP) is steadily rising, leading to a higher risk of mortality. This study assessed the impact of the Weight-Adjusted Waist Index (WWI) on osteoporosis-related mortality.</p> Materials and Methods <p>Data from NHANES 2005–2010, 2013–2014, and 2017–2018 were analyzed to evaluate the relationship between WWI and mortality in osteoporotic patients using weighted proportional hazards model and Kaplan–Meier survival analysis. A subgroup analysis was performed to ensure the stability of the findings.</p> Results <p>The study included 1324 participants. The findings indicated a positive correlation between WWI and OP (OR 1.65, 95% CI 1.45–1.89). Among patients with OP, WWI showed a positive association with all-cause mortality (HR 1.28, 95% CI 1.10–1.48). There was no observed correlation between varying WWI levels and mortality due to cardiovascular disease or cancer.</p> Conclusions <p>Maintaining a lower WWI is associated with a reduced risk of all-cause mortality among individuals with OP.</p>