The aim of this present study is to investigate the influence of warm-up, physical activity level, and body fat percentages on the reaction time of punches and kicks in adult kickboxing practitioners. The sample consisted of 20 kickboxing practitioners. Physical activity level was evaluated by the International Physical Activity Questionnaire-Short Form, body composition by electrical bioimpedance, and reaction time by the mobile application TReaction. The direct punch and the kick with no warm-up had the highest reaction times (p<0.05) when compared with after warm-up and after the two-minute rounds. There were correlations between kick with no warm-up reaction time and fat percentage (r=0.524; p=0.018), and kick with no warm-up and physical activity level (r=-0.560; p=0.010). The physical activity level and the percentage of body fat are variables that interfere with kickboxers’ kick reaction time. Furthermore, the warm-up had a positive influence on the reduction of the reaction time of punches.