<b><i>Introduction:</i></b> As ultrasound becomes more accessible, the use of point-of-care ultrasound examinations performed by clinicians has increased. Sufficient theoretical and practical skills are prerequisites to integrate thoracic ultrasound into a clinical setting and to use it as supplement in the clinical decision-making. Recommendations on how to educate and train clinicians for these ultrasound examinations are debated, and simulation-based training may improve clinical performance. <b><i>Objectives:</i></b> The aim of this study was to explore the effect of simulation-based training in thoracic ultrasound compared to training on healthy volunteers. <b><i>Method:</i></b> A total of 66 physicians with no previous experience in thoracic ultrasound completed a training program and assessment of competences from November 2018 to May 2019. After a theoretical session in ultrasound physics, sonoanatomy, and thoracic ultrasound, the physicians were randomized into one of three groups for practical training: (1) simulation-based training, (2) training on a healthy volunteer, or (3) no training (control group). Primary outcome was difference in the clinical performance score after the training period. <b><i>Results:</i></b> Using a multiple comparison, ANOVA with Bonferroni correction for multiplicity, there was no statistical significant difference between the two trained groups’ performance score: 45.1 points versus 41.9 points (minimum 17 points, maximum 68 points; <i>p</i> = 0.38). The simulation-based training group scored significantly higher than the control group without hands-on training, 36.7 points (<i>p</i> = 0.009). <b><i>Conclusions:</i></b> The use of simulation-based training in thoracic ultrasound does not improve the clinical performance score compared to conventional training on healthy volunteers. As focused, thoracic ultrasound is a relatively uncomplicated practical procedure when taught; focus should mainly be on the theoretical part and the supervised clinical training in a curriculum. However, simulation can be used instead or as an add-on to training on simulated patients.