Mathematical competence in school-related contexts is a multidimensional construct that encompasses several content areas and cognitive components. Kindergarten children have experiences with different types of mathematical content. However, empirical research has focused mostly on children's numerical skills, and less is known about their development in other mathematical content areas and interdependencies between areas, especially when it comes to less-structured approaches to early childhood education. The study investigated two research questions: (1) What is the structure of kindergarten children's mathematical competence? (2) How do the different dimensions of mathematical competence develop over time? One-to-one interviews were completed with 442 kindergarten children to assess their mathematical competence at three measurement points. The results indicate that mathematical competence among kindergarten children should be treated as a multidimensional construct. Furthermore, the results indicate that skills in different content areas affect later skills in the same and in other content areas. Therefore, the results highlight the importance of addressing multiple mathematical content areas in early childhood.