An external focus of attention and autonomy support are identified as key factors to optimize motor learning; however, research in children is limited. Moreover, research has failed to examine these factors in ecologically valid motor learning settings, like physical education. Therefore, the present study examined the effects of external focus of attention when delivered using autonomy-supportive or controlling instructional language on children's motor learning. Thirty-three novice participants (10.30 ± 0.52 years) practiced a land-based curling task under supportive (external-focus instructions delivered with supportive language), controlling (external-focus instructions delivered with controlling language), or neutral (external instructions embedded in the task aim) conditions before completing a retention and transfer test. The supportive group produced higher positive affect after practice and greater accuracy in the retention test compared with the other groups. The findings provide support for the OPTIMAL (optimizing performance through intrinsic motivation and attention for learning) theory of motor learning that combining an external focus and autonomy support conditions improves motor learning.