OBJECTIVE This study aims to examine the associations between various non-insulin-based insulin resistance (nIIR) indices and subclinical atherosclerosis assessed by carotid intima-media thickness (cIMT) in young adults. BACKGROUND nIIR indices, e.g., serum triglycerides (TG) have been reported with an association with cIMT in middle- and old-aged adults. OBJECTIVE We examined the associations of various well-known nIIR indices reported before with cIMT in young adults. METHODS A total of 1,822 young adults free of diabetes in Taiwan were included in 2018-2020. nIIR indices were assessed by TG concentrations, the TyG index, defined as Ln (TG *fasting glucose/2), the TG/high-density lipoprotein cholesterol (HDL-C) ratio, defined as TG divided by HDL-C, and the metabolic score for IR (METS-IR), defined as Ln[(2*fasting glucose)+TG) * body mass index (BMI)/(Ln(HDL-C))]. Multivariable linear regression analyses with adjustments for age, sex, anthropometrics, smoking, alcohol consumption, blood pressure, and total cholesterol were used to determine the associations. For TG only, HDL-C and fasting glucose were additionally adjusted. RESULTS In the overall participants, there was an association between cIMT and TG (β: 0.057, p = 0.04). In subgroup analyses, cIMT was associated with TG (β: 0.127, p = 0.004), the TyG index (β: 0.119, p = 0.01), and TG/HDL-C (β: 0.081, p = 0.03) in the overweight / obese (BMI ≥25 kg/m2), while not in the normal weight individuals. However, cIMT was correlated with TG (β: 0.086, p = 0.01) and TG/HDL-C (β: 0.077, p = 0.01) in those without hyperuricemia, while not in those with hyperuricemia. No association between the METS-IR and cIMT in any young adult subgroups was observed. CONCLUSIONS This study highlights that some nIIR indices could be used to assess cIMT in young adults, particularly for those with obesity and those without hyperuricemia. The TG-based indices instead of the novel marker, METS-IR, are suggestive as stronger predictors of greater cIMT in young adults.