The Unified Modeling Language (UML) has become the de facto standard in object oriented systems design. It has, however, been subject to considerable criticism by analysts due to its complexity and inability to communicate complex systems models. This paper introduces ‘Modular UML,’ a modified presentation and communication format of the UML to more effectively understand multiple UML diagrams as a conceptual model of a complex system. The challenges modular UML are designed to address, the process of developing a modular UML set of exhibits, and an example are discussed.