This open access book presents the results of the project “SysML Workbench for the SPES Methodology” (SpesML), funded by the German Ministry of Education and Research. SpesML is a modeling language that supports the proven SPES methodology by a carefully selected subset of SysML language elements together with a precise semantic interpretation enabling advanced analyses. The book begins with an introduction to the SpesML project in Chapter 1 and the SPES modeling language (SpesML) in Chapter 2. Next, Chapter 3 discusses the introduction of Model-based Systems Engineering (MBSE) in industry and details the challenges faced by industrial practitioners. It also introduces a running example used throughout the book to demonstrate the application and tool implementation of SpesML. Chapter 4 introduces the SPES methodology. Starting with the fundamental principles applied in SPES, it briefly describes the underlying modeling theory and the Universal Interface Model (UIM)concept. Chapter 5 details the subset of language elements of SysML used in SpesML and introduces the concept of expressions as an extension of SysML for formal behavior descriptions. Chapter 6 continues with the realization of the core building blocks in SPES (UIM, viewpoints, granularity layers) through SpesML language elements. Chapter 7 then describes the implementation of a SpesML plugin on top of MagicDraw. Eventually, Chapter 8 introduces three industry case studies, and Chapter 9 concludes with a summary and an outlook. This open access book is written for both researchers in model-based systems engineering and for industry professionals exploiting model-based approaches for systems development. It adds to the development of the SPES methodology described in the three books “Model-Based Engineering of Embedded Systems”, “Advanced Model-Based Engineering of Embedded Systems”, and “Model-Based Engineering of Collaborative Embedded Systems”.