Background: Very preterm infants with patent ductus arteriosus (PDA) are more likely to be born prematurely or receive therapeutic treatments that reduce ductus arteriosus functioning smooth muscle number, reduce the response to oxygen-elicited vasoconstriction, or increase the concentration of circulating vasodilators. Objective: In this study we aimed to evaluate the association between PDA and phototherapy in low birth weight (less than 1500 grams) neonates. Patients and Methods: Between August 2020 and December 2021, 100 neonates admitted to the Al-Hussein Hospital, Al-Azhar University, who needed phototherapy participated in our study. Infants affected with congenital cardiac problems, severe congenital abnormalities, hydrops fetalis, or rhesus isoimmunization required exchange transfusions of blood. After the newborn clinical team established that phototherapy was essential for infants in group A, researcher's secured written approval from the parents.Group (A) involved 50 infants who underwent phototherapy, whereas Group (B) included 50 infants who did not get any phototherapy at all. Results: There was significant difference between Group (A) and B regarding PDA prevalence and ductal size in PDA patients. There is significant difference between the groups as regard L-to-R shunt > small. Conclusion: Phototherapy has been associated to an increased incidence of patent ductus arteriosus in very low and extremely low birth weight infants.