The purpose of this study is to examine the role of Minecraft-based coding activities on computational thinking (CT) of middle school students. In the study, CT was conceptualized so that it encapsulates not only the knowledge of computational concepts (e.g., loops and conditionals) but also the use of CT practices (e.g., testing and debugging). Data were collected using a combination of knowledge of computational concepts tests, the Minecraft-based coding artifacts, and one-on-one student interviews focusing on the processes of developing computational artifacts. The participants were 20 fifth-grade middle school students from a low-income public school with very limited (if none) formal computer programming experiences before the study. The Minecraft-based coding activities were designed and implemented as an instructional program to last 6 weeks. The results of the study showed a statistically significant increase in students' knowledge of computational concepts. Based on the analysis of the students' final coding artifacts, we identified that students mostly used the concepts of sequences, events, loops, and parallelism correctly, whereas variables, operators, and conditionals appeared to be the least successfully used concepts. The qualitative analysis of the artifact-based interviews showed that students employed the CT practices of testing and debugging most of the time while developing an artifact through coding. In contrast, the least resorted CT practice appeared to be reusing and remixing.