Background & Objective: This study aimed to find a biomarker to predict the development of multiple sclerosis (MS). Serum levels of vitamin D3, C-reactive protein (CRP) and melatonin and their ratio were evaluated to find the valuable cut-off point. Methods: Serum levels of vitamin D3, CRP and melatonin were evaluated using commercial ELISA kit in newly diagnosed MS patients and compared with healthy controls. Results: Serum CRP level significantly increased and serum melatonin level significantly decreased in MS patients in comparison to controls. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy for the cut-off point of CRP/melatonin ratio ≥ 78.29087 were 80%. Conclusion: CRP/melatonin ratio ≥ 78.29087 may be used for prediction of MS in an at risk population