The aim of this study was to develop a direct observational system in order to assess competitive behaviours in preschool children. Participants were 176 children (90 boys, 86 girls; M[subscript age]?=?5.2 years) from 10 kindergarten classes of one town of Central Greece. A new observational system (Observational System Assessing Competition in Kindergarten) was developed for the objective measurement of children's competitive behaviours. This system will allow researchers to monitor and evaluate children's competitive behaviour in kindergarten classes. Preliminary direct observation data are presented in order to illustrate the potential uses of the observational system. Results showed that boys express more often competitive behaviours than do girls. Furthermore, the majority of competitive behaviours were observed during organised activities and much less during free activities, breakfast time and discussion.