Deficits in basic skill performance and long-term skill retention among medical students and novice doctors are a persistent problem. This controlled study tested whether the addition of a mastery learning component to simulation-based teaching is associated with long-term retention and performance of peripheral venous catheter insertion. Fourth-year medical students were assigned to receive either the control (simulation without mastery learning,  = 131) or the intervention (simulation + mastery learning,  = 133) instruction in peripheral venous catheter insertion. Performance was assessed at one year post-instruction. Eighty-four students from the control group and 71 from the intervention group participated in the assessment. Students who received the mastery learning instruction achieved higher overall test scores than did controls (median mastery learning score: 20.0, IQR 2.0; median control score 19.0, IQR 3.0; Mann-Whitney U test,  < 0.001, effect size d = 0.82). Pass rates also differed significantly between the groups, with 74.5% ( = 53) of the intervention group passing compared with 33% ( = 28) of the control group ( < 0.001). Mastery learning is an effective means of teaching practical skills to medical students, and is associated with higher scores at a 1-year follow up.