The inhibitory control (IC) is one of the basic executive functions (EFs) that all other EFs are hierarchically perched on this ability. Current knowledge of IC development in the elementary school years is limited. In this study, three tasks; go/no-go task (response inhibition), flanker task (attentional inhibition), and circle-tracing time task (motor inhibition) were administered to investigate sex and age-related differences in IC in 240 children (120 boys) aged 7-12 years preschoolers. Results showed some gender differences in neutral reaction time (RT) in flanker task and go accuracy number in go/no-go task. Also, results suggest the existence of age-related differences in go accuracy number and RT in go/no-go task, neutral RT in flanker task, and motor inhibition index in circle-tracing task that these correlations follow a nonlinear relationship. Our study indicates that IC develop rapidly in the first two years of formal schooling then proceeds at a slower rate.