Objective: Dysregulation of biological rhythm is associated with reduced executive functioning and potentiating psychosis, which are essential for the Theory of Mind (ToM) among patients with schizophrenia. However, the association between cognitive dysfunction, emotional information and disruption of biological rhythm remains uncertain. Methods: Forty-one patients with schizophrenia and forty age, gender and smoking status-matched healthy controls were recruited into the study. The Wisconsin Card Sorting Test (WCST), The Stroop test, The Reading the Mind in the Eyes Test (RMET), The Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) were used. Results: BRIAN total, sleep, activity and social scores were higher in patients with schizophrenia than healthy controls. Higher BRIAN score was correlated with lower RMET score; with higher PANSS total, positive and negative scores, and not correlated with executive functions. In the regression analysis, it was observed that gender and increased BRIAN score was independently associated with lower scores for RMET in a patient with schizophrenia. Conclusion: These results suggest that the disruption of biological rhythm might be associated with ToM in patients with schizophrenia. Future research should examine the relationship between biological rhythm and ToM to determine if any causal associations can be identified.