Background <p>Insulin resistance contributes to hypertension, but the relationship with the novel non-insulin-based metabolic score for insulin resistance (METS‑IR) remains unclear, particularly regarding potential nonlinear patterns.</p> Methods <p>This cross‑sectional study included 1,592 participants. Associations between METS‑IR (continuous and tertiles) and prevalent hypertension were evaluated using logistic regression, restricted cubic splines, and two‑piecewise regression, adjusting for age, sex, lifestyle factors, diabetes, and NAFLD. Subgroup analyses examined effect modification.</p> Results <p>Prevalent hypertension was present in 943 (59.2%). Each 1-unit increase in METS-IR was associated with higher hypertension odds (OR 1.06, 95% CI 1.04–1.08). A nonlinear relationship with an inflection point at 37.58 was identified. Below the inflection point (37.58), each 1-unit increase in METS-IR was associated with a 16.7% higher odds of hypertension (OR 1.167, 95% CI 1.082–1.259); above this point, the association was attenuated but remained significant (OR 1.038, 95% CI 1.007–1.069). Significant interactions were found for sex, BMI, diabetes, and NAFLD.</p> Conclusions <p>METS‑IR is independently and nonlinearly associated with prevalent hypertension, exhibiting a clear threshold effect. It may serve as a practical research indicator, particularly in individuals without overt metabolic disease, though causal inference requires prospective validation.</p>