Background: Patients with acute bronchiolitis are more prone to develop heart failure even in those without underlying cardiac diseases. Clinical assessment of heart failure in such subjects is a challenge. Our objective was to evaluate the diagnostic utility of myocardial performance index and B-type natriuretic peptide (BNP) as predictors of Heart failure during acute bronchiolitis and correlate them to clinical manifestation. Method: 50 subjects with acute bronchiolitis were enrolled in the study over one year duration; 30 healthy subjects of matched age and gender as control group. Heart failure was identified according to clinical, cardiomegaly in X ray and modified ROS classification. We assess the association between clinical manifestations, echocardiographic findings and serum BNP in subjects with bronchiolitis with and without heart failure. Results: 30% of subjects with bronchiolitis developed heart failure. There is significant decreased tricuspid and mitral annular plane systolic excursion and significant increase in pulmonary artery systolic pressure, myocardial performance index (MPI) and BNP during acute bronchiolitis especially among those who developed heart failure. Regression analysis revealed that MPI and BNP are independent predictors of heart failure during acute bronchiolitis. Conclusion: MPI is a valuable echocardiographic marker for early detection of heart failure while BNP is a useful circulating biomarker that can be used to differentiate respiratory distress due to heart failure from pulmonary diseases. It can also be used to estimate the prognosis, as well as to predict cardiac complication in infants presented with acute bronchiolitis