Ectotherm performance and fitness are heavily dependent on environmental temperature. Laboratory exposure to favorable and unfavorable temperatures is used to study these effects, as well as the physiological, biochemical, and molecular underpinnings of variation in thermal performance in many small ectotherms (e.g., insects). It can be challenging, however, to create and manipulate several dynamic thermal environments concurrently in a laboratory setting. Here, we describe the creation and use of a thermal gradient device that can produce a wide range of temperatures that change over time. This device is composed of a solid aluminum plate and copper tubing, combined with a pair of programmable refrigerated circulator baths. This approach avoids the use of multiple heating/cooling baths and makes thermal experiments (e.g., creating a thermal performance or survival curves, quantifying responses to fluctuating thermal environments, or monitoring insect behaviour across a range of temperatures) easier, faster, and more cost-effective. As a proof-of-concept, we used the thermal gradient device to produce a low-temperature survival curve for Drosophila melanogaster in a single experimental run and measured the growth rate of crickets (Gryllodes sigillatus) across a range of temperatures over days at varying amplitudes.