Abstract. The Grid Modeling and Simulation (GridSim) toolkit provides a comprehensive facility for simulation of application scheduling in different Grid computing environments. However, using the GridSim toolkit to create a Grid simulation model can be a challenging task, especially when the user has no prior experience in using the toolkit before. This paper presents a Java-based Graphical User Interface (GUI) tool called Visual Modeler (VM) which is developed as an additional component on top of the GridSim toolkit. It aims to reduce the learning curve of users and enable fast creation of simulation models. The usefulness of VM is illustrated by a case study on simulating a Grid computing environment similar to that of the World-Wide Grid (WWG) testbed [1].