Over the years, mechatronic systems have witnessed an increase in complexity. To address this issue, a model-based approach has been utilized to produce coherent system specification. In model-based engineering, a system is depicted graphically and textually at various levels of granularity and complexity. For this purpose, Systems Modeling Language (SysML) is designed to support development stages in systems, including specification, analysis, design, and validation, and to generate specifications in a single language for use by heterogeneous development teams. Nevertheless, an underlying tool is lacking that would express the totality of a system’s processes and concepts, including mechanical, electrical, and informational aspects. SysML introduces a variety of diagrams and tools that are heterogeneous in notation and terms, e.g., use cases, blocks, activities, components, parameters, sequence, and so forth. This paper proposes a diagrammatic methodology to specify a unified conceptual map for mechatronic systems that can play the role of blueprint for a whole system at different stages of development. The paper focuses on using the proposed methodology as a specification tool, offering a new model that captures the dynamic behaviors of the system. The claim is that this proposed model for specification provides a nontechnical map of the system without a multiplicity of representations as in SysML. To demonstrate the viability of the model, it is applied to a case study of an airport baggage handling system.