Abstract: Background- Neonatal jaundice is commonly seen in preterm new born and phototherapy treatment of choice when indicate. Phototherapy is an efficient treatment although there is some side effect present. These side effect may be on behavioural and physiological in some organ and there is also changes in stages of sleep cycle and circadian rhythm during and after phototherapy for few days. These changes in sleep cycle due to the neurotransmitter tryptophan and there is also changes is hormones like decreased in the growth hormones and there is changes in the melatonin which may affect with sleep cycle. there is some study done which suggestive that phototherapy will affect the stages of sleep but there is solid information available whether there is any effect of phototherapy on cardiorespiratory activity. Some old study is suggestive of there is increased in heart rate and decreased in the SBP systolic blood pressure during phototherapy. Phototherapy cause to increase the respiratory rate and heart rate during phototherapy. Objectives: To determine the outcome of phototherapy after 24hrs, 48hrs, 72hrs, and >72hrs on cardiac function in term neonates with hyperbilirubinemia. ResultsAfter completion of the study we will come to know the effect of phototherapy on cardiac function and also get the idea for how many hours ( <24hrs / 48hrs. 72hrs or > 72hrs) we can give safe phototherapy to the neonate with hyperbilirubinemia without affecting the cardiac function. Or is there any need for cardiac shielding during phototherapy. Conclusion- After completion of the study we will come to know the effect of phototherapy on cardiac function in term neonate who is having neonatal hyperbilirubinemia.