Purpose. The use of virtual reality technology in the field of sports is increasing, but there is a lack of evidence reporting the effects of virtual reality to change the level of mental health and cognitive function in Karate athletes through mixed research methods. This study to determine how virtual reality-based physical activity affected athletes' levels of mental health and cognitive function.
 Material and methods. This study involved male Karate athletes from Cendikia Leadership School in Indonesia (n=30). The athletes were allocated to the experimental group (n=15) and control group (n=15).
 Results. First finding of the quantitative study showed that before the experiment there was no difference in the scores of mental health and cognitive function in the two groups. The second finding showed that there was a difference after the experiment. In qualitative study, athletes revealed their perception that the advantages of virtual reality-based physical activity were fun, easy to implement, and can be carried out without the supervision of a coach. Moreover, they also mentioned the weakness of this tool, namely not all athletes have virtual reality tools, the impact to their eye health, exercise must be carried out in a safe place.
 Conclusions. Thus, this study concluded that physical activity based on virtual reality was proven to be effective in changing of mental health and cognitive function of Karate athletes.