With the emergence of new instructional technologies, pre-service teachers are expected to develop Mathematical Technological Knowledge (MTK), which we define as teacher knowledge of technology developed as a result of exploring mathematics with technology. We examined 16 middle grades pre-service mathematics teachers' (PSMTs) MTK within a geometry course where they used the dynamic geometry software, "Geometer's Sketchpad," as a cognitive tool. The data from this exploratory case study revealed five levels of MTK which can be used to classify the ways PSMTs understand and leverage the capabilities and limitations of this dynamic geometry software. In our conclusion, we recommend mathematics teacher educators attend to PSMTs' different levels of utilizing dynamic geometry software in teaching and learning mathematics. These levels of MTK can also be leveraged to inform mathematics teacher educators' decisions in providing technological experiences within mathematical content and instructional technology courses.