Objective/Background: To examine a novel intervention for nighttime thermal comfort and sleep of perimenopausal- and postmenopausal-aged women who experience hot flashes and insomnia symptoms. Participants: Thirty-nine women (ages 45-58, M = 52.1 years) with sleep-disrupting hot flashes and insomnia symptoms. Methods: This was a 4-week randomized cross-over study. The intervention included 2 weeks of nighttime use of a warming/cooling device worn on the wrist and was compared to a 2-week baseline period (no device). All participants completed questionnaires at the end of each 2-week period, including the Insomnia Severity Index, the PROMIS Sleep Disturbance and Sleep-Related Impairment scales, Epworth Sleepiness Scale, and the Hot Flash Related Daily Interference Scale. Results: The intervention resulted in a reduction in sleep onset latency, as well as an increase in nighttime sleep. There was a significant improvement of scores on the Insomnia Severity Index, PROMIS Sleep Disturbance and Sleep-Related Impairment scales, and the Epworth Sleepiness Scale. Significantly fewer women reported that hot flashes interfered with their sleep (90% vs 70%) and more perceived control over the degree of sleep disruption due to nighttime hot flashes while using the device (5% vs 49%). The majority reported a positive experience, with two-thirds reporting that the device improved their thermal comfort and ability to return to sleep after a night waking. Conclusions: Overall, a thermal comfort intervention may offer sleep benefits for women who experience disruptive nighttime hot flashes, particularly in terms of falling asleep at bedtime and subjective perception of control over nighttime hot flash sleep interference.