Background:Preterm labor is one of the most common pregnancy complications, and it can have catastrophic effects, including preterm birth and accompanying complications. This study’s objective is to compare the efficacy of Magnesium Sulfate and Indomethacin vs Magnesium Sulfate alone in avoiding preterm labor in pregnant women at Kosar Hospital in2019–2021. Methods:In this interventional study, which was conducted as a double-blind, randomized clinical trial on 200 pregnant women with gestational ages ranging from24to32weeks who were referred to Qazvin’s Kosar Hospital. Patients were divided into two equal groups and given magnesium sulfate and indomethacin (group A)or magnesium sulfate alone(group B).The data then was analyzed with SPSS statistical software and statistical tests. Results:According to the study’s findings, the average time interval between receiving the drug and childbirth in group A was774.71+505.91hours and in group B it was545.77+503.32hours,which was statistically significant (P0.05). Besides that, the mean gestational age at the time of pregnancy termination was35.30+250weeks in group A and35.03+2.65weeks in group B, which was not statistically significant (P>0.05).The type of intervention, on the other hand, had a significant relationship with the number of labors during the first 7 days after starting the drug (P >0.05). Conclusion:The results showed that magnesium sulfate and indomethacin were more effective than magnesium sulfate alone in inhibiting and delaying preterm labor.There were similarities in comparing the findings of our study with other studies. Keywords:Preterm labor,Magnesium Sulfate,Indomethacin Financial disclosures:None