As interest in Internet of Things (IoT) technologies has grown, so have concerns and attention to cybersecurity of the newly network-connected products and services offered in many sectors, including energy services, water/waste-water services, automobiles, consumer electronics, and government. This Product Development Cybersecurity Handbook will describe concepts important to developing and deploying secure IoT products for any sector or use case, including discussion of IoT Product architecture, deployment, roles and cybersecurity perspectives. This publication extends and elaborates on NIST’s prior work related to development of IoT products. In addition to discussing the concepts, this publication also demonstrates their application and discusses how satisfaction of cybersecurity in IoT products can be approached.