This book constitutes the refereed proceedings of the First International Workshop on Cyber-Physical Security for Critical Infrastructures Protection, CPS4CIP 2020, which was organized in conjunction with the European Symposium on Research in Computer Security, ESORICS 2020, and held online on September 2020. The 14 full papers presented in this volume were carefully reviewed and selected from 24 submissions. They were organized in topical sections named: security threat intelligence; data anomaly detection: predict and prevent; computer vision and dataset for security; security management and governance; and impact propagation and power traffic analysis. The book contains 6 chapters which are available open access under a CC-BY license.