Processing rational numbers is difficult for many children. The natural number bias is one possible explanation for why children struggle with rational numbers. It refers to the tendency to overgeneralize the properties of natural numbers. In this study, it is argued that in order to be successful in rational number tasks, individuals need to inhibit or suppress their unwanted impulses (in this case the tendency to apply natural number properties). It was investigated whether inhibition plays a role in the occurrence of the natural number bias among primary school children by administering two rational number tasks, two Stroop tasks and a questionnaire measuring inhibitory skills. The results indicated that primary school children were hampered by the natural number bias both in terms of accuracy rates and response times. Additionally, the results did not yield strong evidence for a relationship between inhibition and the occurrence of the natural number bias.