Here, we introduce the Visualization Toolkit for Analyzing Defects in Materials (VTAnDeM). This Python-based software is tailored specifically towards visualizing the stability, phase boundaries, and corresponding defect properties of multicomponent materials. A summary of how VTAnDeM fits into the workflow of computational materials design is illustrated in Figure . We stress that while softwares such as PyLaDa and PyCDT help to automate and post-process first-principles defect calculations, VTAnDeM is intended as a visualization software once the postprocessed results are available. VTAnDeM is an open-source software available and maintained on a Github repository: . In this paper, we use the quaternary diamond-like semiconductor Cu 2 HgGeTe 4 as an exemplary multicomponent material to demonstrate the usage of VTAnDeM. The effects of phase boundaries on the defect formation energetics and resulting carrier concentrations are visualized, and the interactive nature of VTAn-DeM is demonstrated. We encourage that the workflow, analysis, and figures presented here be interpreted as an example of the application of VTAnDeM towards analyzing thermodynamic and electronic properties of materials, especially materials for which defect engineering may tune or alter fundamental properties.