The present study aimed to verify the effect of a warm-up protocol with and without facemask-use on cognitive function. The sample was composed of 17 healthy, non-smoking physical education students (age = 17.6 years, height = 1.71 m, and body mass = 69.7 kg). They were randomized to perform 15 min of warm-up exercises, while wearing a cloth facemask (EXP) or no mask (CON) on two separate occasions, with at least 48-h separating conditions. Rate of perceived exertion (RPE) and d2 Attention assessment were used to verify cognitive function, using a repeated measures general linear model. The warm-up improved cognitive abilities and the results demonstrated significant differences between the EXP vs. CON groups in post-concentration performance (186.06 ± 15.47 EXP-score vs. 178.12 ± 13.66 CON-score), post the total number of errors (23.47 ± 14.50 EXP-frequency < 29.06 ± 13.74 CON-frequency), and in the post RPE (6.0 ± 1.37 EXP-index > 4.7 ± 0.85 CON-index). Wearing a cloth facemask caused positive effects on cognitive function. This data suggests that wearing a cloth facemask during warm-up may stimulate/improve the cognitive function.