Background/Objectives: With the increasing number of households raismg compamon dogs in South Korea, pet tech products and services that use advanced technology to assist in pet care have been developed. However, there are few published studies on smart clothing with temperature control, which is necessary to maintain the health of pets. Therefore, in this study, we developed a temperature-adjustable smart neck gaiter for companion dogs. The main objective of this research is to fabricate smart clothing for dogs that can actively regulate body temperature using Peltier devices that can be cooled and heated. Methods: We designed and manufactured a temperature-adjustable smart textile in the form of a neck gaiter that wraps around the neck, considering the activity and comfort of pets. For the dog's hygiene, nonwashable components, such as Peltier devices and batteries, were also designed to be detachable for repeated washing. We tested the prototype of the temperature-controlled neck gaiter on an actual dog to confirm that it does not cause stress. Results: In this study, a smart neck gaiter that can actively adjust the temperature of dogs was implemented using Peltier devices. The smart neck gaiter is designed to allow dogs to perform various activities without any discomf...