Reaction time (RT) tasks assess several brain functions, and a slow RT can be due to various brain diseases, disorders, and acquired conditions. This study examined age and gender differences in RTs of Spanish preschool children on the ruler drop test (RDT) and presents norm-referenced results. Participants were 3,741 children (1,845 girls and 1,896 boys; mean [M] age = 55.93, standard deviation [SD] = 11.14 months; M body mass index = 15.94, SD = 1.91 kg/m2), selected from 51 schools in southern Spain. We measured RT with the RDT, and we collected both right- and left-hand data. We expressed normative mean RDT values of both hands according to gender and age in percentiles. Based on mean RDT scores, girls exhibited a poorer performance than boys aged 4 years (p = .032, Cohen’s d = − 0.122) and 5 years (p = .001, Cohen’s d = −0.194). For the whole group, RDT performance was faster with increased age, from the age of five years.