This book constitutes the refereed proceedings of the 12th International Conference on Ad Hoc Networks, ADHOCNETS 2020, held in Paris in November 2020. The conference was held virtually due to COVID-19 pandemic. The 19 full papers were selected from 36 submissions covers a variety of network paradigms including mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), vehicular ad hoc networks (VANETs), airborne networks, underwater networks, underground networks, personal area networks, and home networks. It promises a wide range of applications in civilian, commercial, and military areas.