Background <p>Cognitive dysfunction is a core symptom in chronic schizophrenia, yet the mechanisms underlying these impairments remain poorly understood. Thyroid hormones have been suggested to influence cognitive function in various psychiatric disorders, but their role in schizophrenia remains unclear. This study aimed to explore the relationship between thyroid hormone levels and cognitive performance in patients with chronic schizophrenia.</p> Methods <p>A total of 1271 patients with chronic schizophrenia were included in this cross-sectional study. Cognitive function was assessed using the repeatable battery for the assessment of neuropsychological status (RBANS), while thyroid hormone levels (total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), and free thyroxine (FT4)) were measured. Data analysis included linear correlation and regression models to examine the relationships between thyroid hormones and cognitive performance.</p> Results <p>Significant associations were found between thyroid hormone levels and cognitive function. FT3 was positively correlated with visuospatial (<i>r</i> = 0.055, <i>p</i> &lt; 0.05), while TT4 showed a negative correlation with immediate memory, visuospatial, language, and attention (<i>r</i> = -0.109 to -0.068, <i>p</i> &lt; 0.05). Regression analysis further confirmed that TT4 was a negative predictor for immediate memory, visuospatial, language, and attention, while FT3 emerged as a positive predictor for visuospatial.</p> Conclusions <p>This study provides evidence for the role of thyroid hormones in cognitive dysfunction in chronic schizophrenia, with TT4 negatively related to multiple cognitive domains, and FT3 positively associated with visuospatial ability. These findings suggest that thyroid hormone imbalances may contribute to cognitive impairments in schizophrenia and warrant further investigation into potential therapeutic interventions.</p>