Background The benefits of quiet time, a therapeutic method of improving the health care environment, have been evaluated in patients, but only a few studies have examined the effects of quiet time on intensive care nurses. Objective To evaluate the effects of implementing quiet time in a medical-surgical intensive care unit on levels of light, noise, and nurses’ stress. Methods Quiet time consisted of turning down the unit lights for a designated time. Levels of light, noise, and nurses’ stress were measured. Nurses’ stress levels were measured by using a 100-point visual analog scale; unit noise, by using a digital sound level meter (model 407736, Extech Instruments); and unit light, by using an illumination light meter (model 615, Huygen Corporation). Measurements were obtained 30 minutes before and 30 minutes, 1 hour, and 2 hours after implementation of quiet time. Results Analysis of variance and comparisons of means indicated that both light levels and nurses’ stress levels were significantly decreased after quiet time (both P < .001). Noise levels were also decreased after quiet time, but the decrease was not significant (P = .08). Conclusions Use of quiet time resulted in decreased light levels and decreased stress levels among nurses. Quiet time is an easily performed energy-saving intervention to promote a healthy work environment.