Background: Vitamin D deficiency is found to be associated with various cardiac condition. Association of biomarkers of heart failure and Vitamin D level will establish new tool and assessing the prognosis of heart failure. Aim: To study the status of Vitamin D3 level and its correlation with various parameters in heart failure. Material and Method: This study was conducted in F H Medical College and Hospital, Etmadpur, Agra during period of 2 years i.e. July 2019 to July2021. Three hundred patients of heart failure were included in the study and Vitamin D3 level, NT Pro BNP, 2D ECHO, other hematological and biochemical investigation were done. We observed the deficiency of Vitamin D3 (<30mg/dl) in all patients of heart failure and it wasmore significant in class IV (NYHA) heart failure patients. Patients with low vitamin D3 level (<20 mg/dl) had higher pro BNP level of 5352 ng/ml. Ejection fraction was also associated significantly with Vitamin D3 levels. Conclusion: This study was designed to know the effect of Vitamin D3 deficiency in heart failure. We observed that more than 92%. Patients of heart failure were having deficiency of Vitamin D3 level and largest were in NYHA Class IV heart failure patients (P<0.01). We also observed that high level of Pro BNP was significantly associated with low level of Vitamin D3 (P<0.01) i.e. is inversely related. Correlation of Ejection Fraction was significantly associated with Vitamin D3 levels. (P value<0.0001)