Only a few data associated to wearability of facemask during exercise are available in children. The aim of the study was to evaluate the effect of wearing a facemask on perceived exertion (primary aim), dyspnea, physical performance, and cardiorespiratory response during a submaximal exercise test in children aged between 8 and 12 years. This study was performed in 2021 in healthy volunteer children from 8 to 12 years. They performed prospectively two 1-min sit-to-stand tests (STST), with or without a surgical facemask. The perceived exertion (modified Borg scale), dyspnea (Dalhousie scale), heart rate, and pulsed oxygen saturation were recorded before and after STST. The STST measured the submaximal performance. Thirty-eight healthy children were recruited (8–9 years: n = 19 and 10–11 years: n = 19). After the STST, the perceived exertion increased with or without a facemask (8–9 years group: + 1 [0.6; 1.4] and + 1.6 [1.0; 2.1] — 10–11 years group: + 1.3 [0.7; 1.8] and + 1.9 [1.3; 2.6]) and it was higher with the facemask. The difference between the two conditions in perceived exertion was not clinically relevant in any group (mBorgf: 0.56 pts and 0.68 pts, respectively). The different domains of dyspnea assessed with Dalhousie scale were not influenced by the facemask. The submaximal performance measured by the STST was not changed by the mask whatever the age group. The cardio-respiratory demand was not clinically modified.Conclusion: The surgical facemask had no impact on dyspnea, cardiorespiratory parameters, and exercise performance during a short submaximal exercise in healthy children. What is Known: • The use of facemask has been associated with breathing difficulties during physical activities in adults.• Before the COVID-19 pandemic, the facemasks were not recommended during exercise in children and the consequences have been poorly investigated. What is New: • The different domains of dyspnea assessed with Dalhousie scale, the cardiac demand, and the submaximal performance measured by the STST were not changed by the facemask whatever the age group in children.