Background The oral nutrition is big challenge for preterm neonates. Since the best oral feeding method for preterm neonates is not yet known, the present study aimed to evaluate the effect of cup, syringe, and finger feeding methods on reaching the time of full oral feeding and weight gain among preterm neonates. Method This randomized clinical trial study was conducted on 99 preterm neonate’s, born at 30–34 weeks gestation, admitted to the neonatal intensive care unit (NICU) of Al-Zahra and Taleghani Therapeutic-Educational Centers in Tabriz, Iran. Subjects were assigned into finger feeding (n = 33), cup feeding (n = 33), and syringe feeding (n = 33) groups in the allocation ratio of 1:1:1 using block randomization with a block size 6 and 9. They were studied in terms of reaching the time of full oral feeding and weight gain. The data were analyzed using SPSS/version21 software, and ANOVA, chi-square, and ANCOVA tests. Results There was no significant difference in the mean score of reaching the time of full oral feeding among cup, finger, and syringe feeding groups (p = 0.652). The mean score of daily weight gain, oxygen saturation (SaO2), and heart rate after feeding was not significantly different among the three groups (p > 0.05). The effect of confounding variables, including birth weight and age, arterial oxygen saturation, and heart rate before feeding, was controlled. Conclusion Based on the results, one of the cup, finger, and syringe feeding methods can be applied in the NICU, considering the staff’s proficiency in feeding neonates. Trial registration IRCT20150424021917N11.