Previous literature has revealed that visual-spatial processing is associated with both reading and arithmetic. Yet the strength of their relations and the reasons why visual-spatial processing contributes to reading and arithmetic remain ambiguous. The current study focused on two types of visual-spatial skills that recent evidence has suggested are crucial in children’s early reading and arithmetic development: visual-perceptual and spatial visualization skills. With an interval of 6 months, we assessed 104 Hong Kong kindergarten children’s visual-spatial skills, word reading, arithmetic performance, and vocabulary knowledge at Wave 1; orthographic awareness, basic number knowledge, and number line estimation at Wave 2; and Chinese word reading and arithmetic performance at Wave 3. Correlational analysis showed that both visual-perceptual and spatial visualization skills were associated with later Chinese word reading and arithmetic performance. Further mediation analyses revealed that spatial visualization skills, rather than visual-perceptual skills, contributed to Chinese word reading via orthographic awareness and also predicted arithmetic performance through basic number knowledge. However, number line estimation failed to mediate any relations of visual-spatial skills with children’s arithmetic abilities. The results suggest the importance of visual-spatial processing in Chinese word reading and mathematics, with spatial visualization contributing to reading and mathematics for different reasons.