Background: Three-dimensional (3D) printing technology enables the translation of 2-dimensional (2D) medical imaging into a physical replica of a patient's individual anatomy and may enhance the understanding of congenital heart defects (CHD). We aimed to evaluate the usefulness of a spectrum of 3D-printed models in teaching CHD to medical students. Results: We performed a prospective, randomized educational procedure to teach fifth year medical students four CHDs (atrial septal defect (ASD, n = 74), ventricular septal defect (VSD, n = 50), coarctation of aorta (CoA, n = 118) and tetralogy of Fallot (ToF, n = 105)). Students were randomized into printing groups or control groups. All students received the same 20 min lecture with projected digital 2D images. The printing groups also manipulated 3D printed models during the lecture. Both groups answered an objective survey (Multiple-choice questionnaire) twice, pre-and post-test, and completed a post-lecture subjective survey. Three hundred forty-seven students were included and both teaching groups for each CHD were comparable in age, sex and pre-test score. Overall, objective knowledge improved after the lecture and was higher in the printing group compared to the control group (16.3 ± 2.6 vs 14.8 ± 2.8 out of 20, p < 0.0001). Similar results were observed for each CHD (p = 0.0001 ASD group; p = 0.002 VSD group; p = 0.0005 CoA group; p = 0.003 ToF group). Students' opinion of their understanding of CHDs was higher in the printing group compared to the control group (respectively 4.2 ± 0.5 vs 3.8 ± 0.4 out of 5, p < 0.0001). Conclusion: The use of 3D printed models in CHD lectures improve both objective knowledge and learner satisfaction for medical students. The practice should be mainstreamed.