Primary age children are children who are in the age range of 7-12 years and above or in the education system can be called children who are in elementary school age. elementary age children do not have maturity in thinking, children have limitations in sorting and choosing something positive or negative and which has a good or bad impact. One aspect that is very important to know and understand from the development of elementary age children is the cognitive aspect. The purpose of this study was to determine the relationship between cognitive development and learning achievement in school-age children at SD Negeri Kaligoro Kutorejo, Mojokerto Regency. The research design used correlation analytic using a cross sectional approach. The population in this study were grade III to fifth grade students at SD Negeri Kaligoro Kutorejo, Mojokerto Regency, totaling 92 students. A sample of 75 respondents was taken using proportional random sampling technique. data using primary data through instruments and documentation to view report cards. The results showed that from 75 respondents, there were 8 respondents (10.7%) cognitive development with sufficient category, and 67 respondents (89.3%) cognitive development with strong category. The results showed H0 was rejected and H1 was accepted, which means there is The relationship between cognitive development and learning achievement in school-age children at SDN Kaligoro Kutorejo Mojokerto, which is indicated by the p value (0.000) < (0.05) with the level of closeness of the relationship is not strong indicated by the correlation coefficient value of 0.000. The direction of the relationship between variables is not in the same direction as indicated by a negative sign on the correlation coefficient of cognitive development with learning achievement in school-age children, which means that the better the cognitive development of children, the higher the learning achievement of school-age children.