Background: Creating a womb-like environment for the preterm infant is vital to reduce the stress caused by stimuli and facilitate optimal neurological-behavioral development. Purpose: This randomized-controlled study aimed to determine the effect of simulative heartbeat nest use on vital signs, pain level, and comfort in preterms. Methods: The study population consisted of 52 (experiment: 25, control: 27) preterms hospitalized in a university hospitals neonatal intensive care unit between May & ndash;November 2018. Before the application, preterms in both groups were evaluated with PIPP and Comfort scales. The experiment group was monitored in the nest with a heart beating device for 15 min. The control group was observed in the nest without the device for 15 min. Their heartbeats and oxygen saturation were recorded. After the application, preterms in both groups were re-evaluated with PIPP and Comfort scale. Results: There was no statistically significant difference between the groups in terms of gestation week, age, birth weight and height, HB, SaO2, PIPP, and Comfort Scale total scores before and after the application (p > .05). However, the mean SaO2 increased significantly during the application (p < .003) in the experiment group; and that the PIPP total score decreased statistically significantly (p: 0.001) after the application. The comfort scale total score averages of the preterms in both groups decreased statistically significantly after the application (experiment:p <.01; control:p < .05). Implications for practice and research: Preterms in both groups had similar indicators. The nests that create heartbeat provide positive outcomes, such as the standard nests. (c) 2021 Elsevier Inc. All rights reserved.