The relationship between focus of attention instructions and motor performance is a topic of significant research interest. It is widely accepted that attending to the mechanics of the movement when performing a motor task (internal focus) yields poorer performance and less effective movement organization than attending to the movement outcome (external focus). Specifically, an external focus is suspected to promote more flexibility in the motor system, inducing more effective muscular activity and movement kinematics, which are mechanisms directly responsible for organization of the resulting movements. However, no review has systematically assessed the influence that focus of attention instructions have on muscular activity and movement kinematics. The purpose of this systematic review was to examine evidence on the effect that focus of attention instructions have on the underpinning mechanisms of movement organization. Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, a comprehensive electronic literature search yielded 36 research studies. Using a narrative methodological approach, the findings were thematically analyzed and synthesized. Generally, external focus of attention instructions resulted in muscular activity and movement kinematic profiles that reflected more effective movement organization than those resulting from the provision of internal focus instructions, thus supporting a central tenet of the constrained action hypothesis.