This book constitutes the refereed proceedings of the 14th International Workshop on Constructive Side-Channel Analysis and Secure Design, COSADE 2023, held in Munich, Germany, during April 3-4, 2023. The 12 full papers included in this book were carefully reviewed and selected from 28 submissions. They were organized in topical sections as follows: fault-injection analyses and countermeasures; side-channel analyses and countermeasures; attacks on PQC and countermeasure; and analyses and tools.