The Optimizing Performance Through Intrinsic Motivation and Attention for Learning theory postulates that directing attention to the intended movement effect or outcome (external focus) is more effective than directing attention to the internal body motion or body part (internal focus). This study compared external vs internal focus of attention as novice students learned ultrasound-guided peripheral cannulation. The authors hypothesized that conditions promoting an external (vs internal) focus of attention would result in better performance on immediate and delayed (retention) testing. The authors conducted a randomized, experimental study from October 2022 to February 2023 comparing external and internal focus using ultrasound-guided peripheral venous cannulation followed by practice using an ultrasound training block. Undergraduate health science students performed 4 practice trials with instructions to focus on the needle tip (external focus) or their hands (internal focus), followed by an immediate assessment and a retention assessment 2 weeks later. The primary outcome was time to successful cannulation. Results were compared using Kaplan-Meier curves and parametric survival analysis regression (accelerated failure time) models. Seventy participants completed the immediate assessment. The external focus group completed successful cannulation a mean of 2.33 times faster (95% CI = 1.47, 3.67; P < .001) than those in the internal focus group (median time, 12.0 vs 29.5 seconds). Results also favored the external focus group during practice, with the external focus group successfully completing the task a mean of 1.83 times faster (95% CI = 1.04, 3.21; P = .04) than the internal focus group. In the retention assessment, the external focus group successfully completed the task a mean of 2.37 times faster (95% CI = 1.19, 4.74; P = .02) than the internal focus group. External focus of attention compared with internal focus of attention improves medical motor skill learning in novice learners.