Objectives <p>The relationship between blood cadmium levels and the risk of periodontitis remains unclear. This study aimed to explore the association between blood cadmium concentrations and periodontitis in a large sample of the U.S. population from 2011 to 2014.</p> Methods <p>This cross-sectional study analyzed data from 5215 participants in the National Health and Nutrition Examination Survey (NHANES) 2011–2014. Blood cadmium levels were the exposure variable, and periodontitis was the outcome variable. Multivariate logistic regression and a two-piecewise linear regression model were used to examine the nonlinear relationship between blood cadmium levels and periodontitis. Stratified analyses were conducted to identify subgroups at higher risk.</p> Results <p>The study identified a nonlinear relationship between blood cadmium levels and periodontitis risk. The threshold effect was observed at 0.37 µg/L and 1.20 µg/L. When blood cadmium levels were below 0.37 µg/L, the odds ratio (OR) for periodontitis was 0.88 (95% CI: 0.31, 2.48; p = 0.81). For cadmium levels between 0.37 and 1.20 µg/L, the OR increased significantly to 12.40 (95% CI: 2.77, 55.57; p &lt; 0.001). When cadmium levels exceeded 1.20 µg/L, the OR decreased to 0.45 (95% CI: 0.06, 3.39; p = 0.44).</p> Conclusions <p>The study found a nonlinear association between blood cadmium levels and periodontitis risk in U.S. adults. The risk of periodontitis increased significantly when blood cadmium levels were between 0.37 and 1.20 µg/L.</p>