Previous investigations on the impact of oral zinc sulfate treatment on newborns' serum bilirubin levels have produced conflicting results. As a result, the goal of this clinical study was to evaluate how oral zinc sulfate affected the levels of serum bilirubin in term infants who were admitted to the neonatal intensive care unit. The study was conducted at the Neonatal Care Unit of Besat Hospital in Sanandaj, Kurdistan Province, as a double-blind randomized controlled trial. The participants included term infants (37-42weeks of gestation) who required phototherapy and were admitted to the neonatal intensive care unit. A total of 290 infants were enrolled and randomly divided into two groups. The intervention group received oral zinc sulfate supplementation at a dosage of 1mg/kg per day in addition to phototherapy, while the placebo group received an equivalent amount of placebo daily. Bilirubin measurements were obtained at the initiation of the intervention and subsequently every 24h until discharge. The collected data were analyzed using STATA software version 17. After the infants were randomly allocated to the zinc-sulfate and placebo groups, the study outcomes, including the average changes in bilirubin levels after intervention, the hours of phototherapy, and the number of days of hospitalization, were analyzed and compared for a total of 160 infants in the zinc sulfate group and 130 infants in the placebo group. The reduction in bilirubin levels in infants receiving zinc sulfate was (- 3.75 ± 0.19 CI 95% - 4.12, - 3.37) and for placebo group was (- 1.81 ± 0.15 CI 95% - 2.12, - 1.50) 24h after the intervention. Furthermore, 48 and 72h following the intervention, bilirubin levels in the intervention group demonstrated a more substantial decline. The zinc sulfate group had a shorter hospital stay (2.13 ± 0.04 vs. 2.83 ± 1.42) and required less phototherapy hours than the placebo group (6.21 ± 2.16 vs. 8.78 ± 1.40). Conclusions: Oral zinc sulfate supplementation in term neonates with hyperbilirubinemia decreased the level of bilirubin levels, duration of phototherapy, and hospital stay. Trial registration: IRCT, IRCT20220806055625N1. Study Registered 25 December 2022, http://irct.ir/trial/66,722 .