Diet is a key modifiable risk factor for non-communicable diseases, yet evidence linking macronutrient intake to mental health—particularly anxiety—remains limited. Understanding these associations may provide insight into potential preventive strategies.This study examined the association between macronutrient-based dietary patterns and mental health outcomes, including moderate-to-severe anxiety and suicidal ideation, and explored potential sex-specific differences using nationally representative data.We analyzed 9,002 adults aged ≥19 years from the 2021–2023 Korea National Health and Nutrition Examination Survey. Dietary patterns were categorized as normal, high-carbohydrate (HCHO), high-fat (HF), or high-protein (HP) based on macronutrient energy proportions. Anxiety was assessed using the GAD-7 (≥10), and suicidal ideation was identified through self-report. Complex-survey logistic regression with sequential covariate adjustment was employed, including sex-stratified models.Dietary patterns were not associated with suicidal ideation. However, individuals in the HP group had significantly lower odds of moderate-to-severe anxiety compared with the normal-diet group (adjusted OR 0.49, 95% CI 0.30–0.81). In sex-stratified analyses, this inverse association remained significant only in men (OR 0.23, 95% CI 0.09–0.60). No significant associations were observed in women. Higher anxiety scores were strongly associated with suicidal thoughts, planning, and attempts.The association between high protein intake and lower anxiety may relate to increased availability of amino acids involved in neurotransmitter synthesis and stress regulation. The stronger effect observed in men suggests possible sex-specific metabolic or hormonal influences. However, the cross-sectional design limits causal interpretation, and dietary quality within macronutrient categories was not evaluated. Despite these limitations, the findings indicate that dietary composition—particularly protein intake—may be a modifiable factor linked to anxiety risk.High-protein dietary patterns were associated with reduced odds of moderate-to-severe anxiety among Korean adults, especially men. Although no relationship was found between dietary patterns and suicidal ideation, the strong association between anxiety severity and suicide-related behaviors highlights the importance of identifying modifiable contributors to anxiety. Longitudinal studies are needed to clarify causality and underlying mechanisms.