This book constitutes the thoroughly refereed post-conference proceedings of the 4th International Conference on Industrial IoT Technologies and Applications, IoT 2020, held in December 2020. Due to Covid-19 pandemic the conference was held virtually. The widespread deployment of wireless sensor networks, clouds, industrial robot, embedded computing and inexpensive sensors has facilitated industrial Internet of Things (IndustrialIoT) technologies and fostered some emerging applications. The 14 carefully reviewed papers are a selection from 28 submissions and detail topics in the context of IoT for a smarter industry.