Usability studies on simulations within 3-Dimensional Virtual Worlds (3D VW) have challenges and features that are unique compared to a traditional usability study on a website, mobile app, or even a 3D VW itself. The locus of control is not the 3D VW, but rather the content created within the 3D environment, i.e., the simulation. This chapter reviews the challenges and features that are unique to usability studies of 3D VWs. Drawing from previous literature and a study to evaluate the usability of the Crafter’s Ear simulation within Minecraft (Espinosa, 2019), this chapter examines concepts and examples from usability studies done within 3D VWs to propose a conceptual model for usability studies designed for 3D VW simulations.