In this 3-year longitudinal study, we examined the interplay of children's motivational orientations, spontaneous focusing on numerosity (SFON) and number sequence and arithmetical skills from kindergarten (at age 6) to grade 1 (at age 7). We also examined the direct and indirect contributions of motivation and SFON to the acquisition of arithmetical skills from grades 1 to 2 (at age 8). The study involved 136 Finnish-speaking, typically developing children. Teacher ratings were used to assess the children's motivational orientations (i.e., task orientation, task avoidance orientation and social dependence orientation) in kindergarten and grade 1. Number sequence skills and SFON were evaluated in kindergarten, and arithmetical skills were assessed in kindergarten, grade 1 and grade 2. A theoretical model of the relationships among the variables was proposed, and the associations were analysed using path analysis. The results showed that task orientation, social dependence orientation and task avoidance orientation were each unique predictors of later arithmetical achievement. Furthermore, together with arithmetical skills in grade 1 and counting abilities in kindergarten, they helped to predict arithmetical achievement in grade 2. Motivational orientations did not explain the significant contributions of SFON to later arithmetical skills. The study suggests that both motivational orientations and SFON require attention and scaffolding in educational contexts, such as assessment and teacher-child interaction from early on.