Different body positions have different effects on the health status of preterm neonates. However, the results of the previous studies are an area of ongoing doubt. In this regard, a study was undertaken to evaluate the effect of left lateral positioning versus right lateral positioning on gastric emptying and selected physiological parameters in terms of heart rate, respiratory rate, and oxygen saturation among neonates admitted in NICU/SNCU [SNCU: Sick Newborn Care Unit, NICU: Neonatal Intensive Care Unit] of Medical Colleges and Hospitals in Kolkata, West Bengal. The conceptual framework adopted for the study was the 'Prescriptive model'. Among the population of admitted neonates, 45 neonates were selected as samples, by using non-probability purposive sampling (Left lateral group-15, Right lateral group-15, and Control group-15). A quasi-experimental time-series design was used. Ethical permission was taken from Institutional Ethics Committee. 5 ml disposable syringe, pulse oximeter, and record sheet were used as the tool. Final data has collected from October 2019 to December 2019. On each observation day, gavage feeding was given to the neonates. After feeding, they were placed in the left lateral position (Exp-I) and right lateral position (Exp-II). After 2 hrs. of positioning, at first, physiological parameters were assessed. Then, the gastric residual volume was measured and recorded. The result revealed from ANOVA that, in the right lateral position the gastric residual volume was less, than the left lateral position in all the observations, which is evident from 'F' value [F=3.290*,4.942*,3.365*]and [F=8.546*,7.986*,9.620*] at P<0.05. But, there were no significant differences in physiological parameters. Furthermore, 't' value df (28)=1.70 p<0.05 also showed a significant difference in gastric residual volume between the two groups. The study concludes that gastric emptying is faster in right lateral position than the left lateral position; and, no effect of any position on physiological parameters. The study has great implications in nursing practice by placing the neonate in the right lateral position after feeding for adequate gastric emptying. A similar study can be conducted with a larger sample and with a different study design for generalization.