Background: One of the most serious complications of pregnancy is preterm labor (PTL) and delivery. Further, there are different tocolytic agents available to enhance the time of delivery. Objectives: The aim of this study was to compare the effectiveness of transdermal nitroglycerin (glyceryl trinitrate, GTN) and oral nifedipine for managing preterm labor. Patients and Methods:This was a randomized clinical trial involving women who were admitted to our hospital with a diagnosis of PTL. Group one received transdermal GTN, whereas group two received oral nifedipine. All vital signs, fetal heart rate (FHR), contractions, dilation, and effacement, as well as gestation age at the time of delivery, have been monitored and evaluated in both groups of patients. Our main goal was the postponement of delivery so as to secure the most beneficial effect of primary corticosteroid administration for the fetus. Results: Both groups were matched regarding age, gestational age at the time of tocolytic therapy, height of fundus, history of pregnancy, abortion, delivery, and stillbirth, primary body temperature, and systolic and diastolic blood pressure. Those who received GTN had a more prolonged delay of delivery. Also, the GTN group had infants with better one-and five-minute Apgar scores. Although both groups reported minimal side effects, tachycardia and nausea were reported more frequently in GTN patients. Conclusions: Transdermal GTN was shown to be more effective in controlling PTL compared to oral nifedipine in terms of both maternal and neonatal effects.