This book constitutes the refereed post-conference proceedings of the 4th EAI International Conference on Innovations and Interdisciplinary Solutions for Underserved Areas, InterSol 2020, held in Nairobi, Kenya, in March 2020. Due to the COVID-19 pandemic the conference is postponed to a later date in 2020. The 20 papers presented were selected from 50 submissions and issue different problems in underserved and unserved areas. They face problems in almost all sectors such as energy, water, communication, climate, food, education, transportation, social development, and economic growth.