Research Findings: This study investigates the role of fine motor and mathematics instruction in mathematics achievement in an international sample of kindergarteners from the United States and China. Multilevel modeling was used to assess the interaction between students' entering skills and classroom time spent on basic math, higher-order math and fine-motor instruction. For American children, the effect of basic math and higher-order math instruction on student achievement depended on entering skills; however, fine motor instruction had negative average effects on student achievement and did not depend on students' entering skills. Instruction time was not a significant predictor of achievement for Chinese students. Practice or Policy: Though fine motor skills have a robust correlation with mathematics achievement, a causal link has not been established. Our study indicates that time spent in fine motor instruction does not advance mathematics achievement in kindergarten and in fact may weaken mathematics achievement, given the limited time in the instructional day. American teachers in our sample who spent more time in fine-motor instruction tended to spend less time on basic math and higher-order mathematics instruction. Educators should weigh instructional trade-offs carefully and work to tailor instruction to students' skill levels.