Background: Basic thoracic ultrasound is being used more frequently by clinicians in several settings due to its high diagnostic accuracy for many common causes of respiratory failure and dyspnoea. However, ultrasound examinations are operator-dependent, and sufficient competences are needed to obtain high sensitivity and specificity of examinations. Additionally, it is crucial for ultrasound operators to perceive the competence to interpret the images and integrate them into the patient history and other examinations. This study aims to explore and gather validity evidence for an objective structured clinical examination test of basic thoracic ultrasound competences and establish a pass/fail score. Methods: An expert panel created the test which included two theoretical and five practical stations representing cases with different diagnoses that cause respiratory symptoms and which are possible to establish by basic thoracic ultrasound. Twenty-five participants with different levels of experience in basic thoracic ultrasound completed the test. Data of the test scores were used for item analysis, and exploring validity evidence was done according to Messick’s framework which is recommended. The contrasting groups' standard setting method was used to establish a pass/fail score. Results: The summarised internal consistency reliability was high with a Cronbach’s alpha of 0.87. The novice group (n = 4) had a mean test score of 42 ± 10.1 points, the intermediate group (n = 8) scored 79.1 ± 8.1 points, and the experienced group (n = 13) 89.0 ± 6.2 points (one-way ANOVA, p < 0.001). A pass/fail score of 71 points was thus derived (maximum test score = 105 points). Conclusion: We developed a test for the assessment of clinical competences in basic thoracic ultrasound with solid validity evidence, and a pass/fail standard with no false positives or false negatives.