This study compared the effects of mental practice, physical practice, and no practice on the performance and retention of a novel throwing task. Research supports the effectiveness of mental practice on performance; however, retention of learning has not been adequately investigated. Participants were 152 students ages 18 to 44 years (M = 20.5, SD = 2.9), who completed a pretest, posttest, and five-week delayed retention test of dart throwing with the nonpreferred hand. In the practice phase, participants completed 50 mental practice or physical practice trials of the darts task or 50 trials of a catching task. Results indicated that overall scores increased from pretest to posttest and retention test, and decreased from posttest to retention test, but that these effects did not differ for type of practice. The findings suggest equal learning and retention of learning for novel throwing tasks for control, mental practice, and physical practice conditions; however, further research that considers issues raised is recommended.