Introduction: Obestatin is a gastrointestinal-peptide hormone which influences glucose and lipid metabolism, body weight and energy homeostasis. Very little is known about the association between gut peptides and thyroid diseases. The aim of the present study was to investigate the association between serum concentrations of obestatin and thyroid function in subclinical hypothyroid and hyperthyroid subjects. Materials and Methods: This study was performed on 35 hypothyroid, 35 hyperthyroid and 35 euthyroid subjects (controls) who referred to the Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences. In all participants, serum levels of obestatin, TSH, FT3, FT4, insulin, glucose as well as BMI were assessed. Serum obestatin, FT3, FT4 and TSH were measured by ELISA, Electrochemi­luminesc­ence immunoassay (ECLIA) and Immunoradiometric assay (IRMA), respectively. Data were analyzed by T-test, One-Way ANOVA and Pearson correlation using SPSS 16. Results: Serum concentrations of obestatin in both hypothyroidism and hyperthyroidism (0.04±0.01 and 0.05±0.02 ng/ml respectively) were significantly lower than in the control group (0.09±0.01 ng/ml), (P-value < 0.001). No significant correlations were observed between serum levels of obestatin and FT3, FT4, and TSH.  Conclusion: Our results indicated obestatin concentrations were significantly associated with thyroid function.