With the growing complexity of software and in particular of software-reliant systems and systems-of-systems, the focus of cybersecurity on network and code has been increasingly shifted to design and more recently to “cybersecurity by design” or “design for cybersecurity”, where the software architecture is the keystone for enforcing cybersecurity. Early evidence of cyber risks, attacks and vulnerabilities enables efficient and effective cybersecurity solutions. Security measurement of software architectures is needed to produce sufficient evidence of cybersecurity level in the design phase. Moreover, software architectures have to support runtime security measurement to obtain up-to-date cybersecurity information. This is essential for self-protecting systems and self-adaptive cybersecurity solutions. This International Workshop on Designing and Measuring CyberSecurity in Software Architecture (DeMeSSA 2019) at ECSA 2019, will provide researchers and practitioners with a forum to exchange ideas and experiences, analyze research and development issues, discuss promising solutions, and propose inspiring visions for the future in complementary fields of Cybersecurity from the perspective of the Software Architecture: Designing CyberSecurity in Software Architecture and Measuring CyberSecurity in Software Architecture Design.