The role of diet-induced acid-base imbalance in insulin resistance (IR) and related cardiometabolic abnormalities has attracted considerable attention. This study sought to investigate the association between dietary acid load and IR indices among Iranian adults. The study included 6,531 participants, with dietary acid load estimated using a validated questionnaire which comprised 65 food frequency items. The IR indices assessed included: Triglyceride to high-density lipoprotein (TG: HDL), Metabolic score for insulin resistance (METS-IR), Triglyceride Glucose-Body mass index (TyG-BMI), Triglyceride glucose (TyG), and Triglyceride glucose-waist circumference (TyG-WC). The results revealed that all IR indices were significantly higher in participants positioned in the top tertiles of dietary acid load as opposed to those in the lowest, with a notable increasing trend (p < 0.001). Using a crude model, there was a significant positive association between TG: HDL, TyG, TyG-WC, TyG-BMI, and METS-IR with dietary acid load (p < 0.001). However, in the fully adjusted model, only TyG and TyG-WC remained significant (OR=1.16, 95% CI: 1.04-1.30, and OR=1.69, 95% CI: 1.51-1.90, respectively). In summary dietary acid load is significantly associated with IR indices, with TyG-WC showing the strongest relationship.