This chapter examines what is known about the neurocognitive mechanisms underlying motor imagery practice in sport. It provides a brief overview of the experimental paradigm by which motor imagery practice is typically studied in sport and outline some representative findings from this approach. The chapter explores motor simulation theory to explain some plausible neurocognitive mechanisms underlying motor imagery practice effects. It provides some potentially fruitful new directions for motor imagery research in sport. Motor imagery “scripts” are typically used during training and practice to guide the cognitive simulation of an action. Motor imagery practice can improve the learning and performance of a variety of sports skills. Although several possible explanations of motor imagery effects have been proposed since the 1930s, none is as comprehensive as that which emerges from motor simulation theory.