Are there differential benefits of training sequential number knowledge versus spatial skills for children's numerical and spatial performance? Three- to five-year-old children (N = 84) participated in 1 session of either sequential training (e.g., what comes before and after the number 5?) or non-numerical spatial training (i.e., decomposition of shapes). Children who received sequential training showed near transfer to a number ordering task and far transfer to a number line task. Furthermore, these children showed more improvement on the version of the number line task where a midpoint reference was presented (i.e., at 5) than on the version without a midpoint. Before the training, the midpoint reference did not enhance performance. In contrast, although children who received non-numerical spatial training showed near transfer to a 2-D mental transformation task, they did not show transfer to number ordering or number line tasks, even though spatial skills were correlated with performance on these tasks. These results support the view that knowledge of sequential relations among successive numbers is an important aspect of children's early numeracy knowledge in tasks that require ordinal understanding of numbers from 1 to 10 and support the educational importance of developing numerical activities that enhance children's understanding of these relations.