Background <p>Diabetic kidney disease (DKD) has a substantial impact on the quality of life and life expectancy of individuals with type 2 diabetes (T2D). Magnesium plays a crucial role in regulating blood glucose levels and insulin sensitivity, yet the association between dietary magnesium intake and DKD remains unclear. This study aims to investigate the association between dietary magnesium intake and DKD among American adults with type 2 diabetes.</p> Methods <p>This cross-sectional study utilized data from the National Health and Nutrition Examination Survey spanning the years 2005–2018. Multivariable regression models were employed to explore the association between dietary magnesium and DKD. Additionally, restricted cubic spline and threshold effect analysis were conducted. Stratified analyses and sensitivity analyses were performed to verify the robustness of the findings.</p> Results <p>The study included 6,032 participants with T2D, of whom 38.4% (2,316/6,032) were concurrently diagnosed with DKD. Compared to the group with lower dietary magnesium intake (Q1, ≤ 180&#xa0;mg/day), the adjusted odds ratios for DKD in the higher intake groups Q2 (181.0-250.0&#xa0;mg/day), Q3 (251.0-341.0&#xa0;mg/day), and Q4 (≥ 342.0&#xa0;mg/day) were 0.86 (95% CI: 0.73–1.02, <i>P</i> = 0.086), 0.71 (95% CI: 0.59–0.86, <i>P</i> &lt; 0.001), and 0.70 (95% CI: 0.55–0.90, <i>P</i> = 0.005), respectively. The association between dietary magnesium intake and DKD exhibited a non-linear curve (non-linear, <i>P</i> = 0.029), with an inflection point approximately at 300&#xa0;mg/day.</p> Conclusions <p>This cross-sectional study reveals that dietary magnesium intake was inversely associated with DKD, with an inflection point approximately at 300&#xa0;mg/day. Further research is necessary to validate these findings.</p>