This study aimed to test whether a mental rotation skills (MRS) training intervention could improve MRS speed and effectiveness, and determine if expected gender differences occurred. Students were randomly assigned to intervention or control groups. The intervention group completed an online MRS training tool while the control group did not. Results showed a small improvement in MRS for the intervention group, but it was not statistically significant. There was also an inconclusive potential gender effect. The training tool was enjoyable but challenging. Further research is needed with modifications to better measure any effects.