This study investigates the association between the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and suicidal ideation in adults using data from the National Health and Nutrition Examination Survey (NHANES) conducted in the United States from 2005 to 2016. The NHHR, calculated as the proportion of HDL-C to non-HDL-C, was assessed using the Patient Health Questionnaire-9's ninth item, which evaluates suicidal ideation. The study included 29,288 participants, with 3.82% reporting suicidal ideation. Multivariate logistic regression analysis revealed that elevated NHHR levels were significantly and positively associated with an increased likelihood of suicidal ideation (odds ratio [OR] = 1.06, 95% confidence interval [CI]: 1.02–1.11; P = 0.0048). This relationship remained consistent after adjusting for various confounding factors. Subgroup analysis and interaction tests showed no significant influence of age, sex, race, BMI, education level, marital status, hypertension, diabetes, and smoking status on the positive relationship. An inverted U-shaped curve was observed in non-smokers, with the inflection point at 7.80. The findings suggest that NHHR may serve as a predictive indicator of suicidal ideation, highlighting its potential utility in risk assessment and preventive strategies.This study investigates the association between the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and suicidal ideation in adults using data from the National Health and Nutrition Examination Survey (NHANES) conducted in the United States from 2005 to 2016. The NHHR, calculated as the proportion of HDL-C to non-HDL-C, was assessed using the Patient Health Questionnaire-9's ninth item, which evaluates suicidal ideation. The study included 29,288 participants, with 3.82% reporting suicidal ideation. Multivariate logistic regression analysis revealed that elevated NHHR levels were significantly and positively associated with an increased likelihood of suicidal ideation (odds ratio [OR] = 1.06, 95% confidence interval [CI]: 1.02–1.11; P = 0.0048). This relationship remained consistent after adjusting for various confounding factors. Subgroup analysis and interaction tests showed no significant influence of age, sex, race, BMI, education level, marital status, hypertension, diabetes, and smoking status on the positive relationship. An inverted U-shaped curve was observed in non-smokers, with the inflection point at 7.80. The findings suggest that NHHR may serve as a predictive indicator of suicidal ideation, highlighting its potential utility in risk assessment and preventive strategies.