Aim This study was carried out to investigate the relationship between the negative automatic thoughts of patients with schizophrenia and their levels of social functionality. Design and Methods This cross‐sectional study was conducted 142 patients with schizophrenia. The data were collected using the Personal Information Form, Negative Automatic Thoughts Questionnaire (NATQ) and Social Functioning Assessment Scale (SFAS). Findings There was a strong negative correlation between the mean scores obtained from the overall NATQ and SFAS. In addition, negative automatic thoughts of the patients with schizophrenia had a negative effect of 47.2% on their social functionality. Practice Implications It was found that the patients had moderate levels negative automatic thoughts and social functionality; and that their negative automatic thoughts affected their social functionality negatively.