Children diagnosed with cerebral palsy (CP) often show difficulties in arithmetic compared to their typically developing peers. The present study explores whether cognitive and motor variables are related to arithmetic performance of a large group of primary school children with CP. More specifically, the relative influence of non-verbal intelligence, working memory, word decoding capacities, gross- and fine motor skills on arithmetic performance is examined using structural equation modeling. One-hundred sixteen primary school children with a formal diagnosis of CP participated (76 males, M = 7; 3 years, SD = 3 months). In agreement with previous studies our results showed that the cognitive and motor predictors were all positively correlated to each other. Furthermore, in the cognitive model, non-verbal intelligence and word decoding were related to arithmetic in primary school. Our combined model (that included both motor and cognitive variables) showed that word decoding and fine motor skills were the strongest predictors of arithmetic performance. To conclude, this study was the first to show the influence of word decoding and fine motor skills on arithmetic performance of children with CP. (Contains 3 tables and 1 figure.)