For the past 40 years considerable attention has been devoted to the innovation, characterization, and implementation of polymer heat exchanger technology, driven by the corrosion resistance, low density, low cost, and ease of manufacture of many polymeric materials. Moreover, new polymer composites, with higher impact and yield strengths, higher temperature limits, and higher thermal conductivities, promise to bridge the performance gap that exists between polymers and corrosion-resistant metals. This paper begins by reviewing the history of polymer heat exchangers and the technical limitations that have motivated much of the research on this technology. The notable developments that have taken place in the last decade and primary potential applications for polymer heat exchangers are then discussed, including solar water heaters, heat recovery systems, and seawater heat exchangers, in particular, for the desalination industry. The paper closes with a review of compact polymer heat exchangers, with millimeter-sized passages, and thoughts on future applications of this most promising technology.