This qualitative study examined middle school students' performance, solution strategies, difficulties and the underlying reasons for their difficulties in calculating the volume of a rectangular prism. The data was collected from 35 middle school students (6th, 7th and 8th grade students) enrolled in a private school in Istanbul, Turkey. The data was obtained from a questionnaire involving 3 problems and one-to-one semi-structured interviews with all the participants after the application of the questionnaire. The results revealed that the students had a moderate level of performance in terms of calculating the volume of a rectangular prism. Moreover, the analysis showed that students were able to create a limited number of solution strategies for the given problems. In addition, some students were not able to correctly calculate the volume of a rectangular prism and they had difficulties in calculating the volume of a rectangular prism. A discussion of findings and recommendations for future research studies are given.