Although an understanding of fractions is a critical precursor for other mathematical concepts, surveys of math education in the U.S. indicate that school-age children lack age-appropriate math skills. Thus, understanding the critical precursors of fraction knowledge is important for the development of instructional materials. The aim of the present study was to examine whether instructional format affected children’s learning and transfer of fractions. Six- to 8-year-old children participated in a longitudinal study (pre/post design) in which they received a fraction-training intervention. We manipulated the extent to which real-world instruction was grounded in visual vs. symbolic representations. We find that 1st and 2nd graders were able to learn fraction concepts following this intervention and that the extent to which the instructional stimuli were grounded in visual vs. symbolic representations affected children’s proportional reasoning knowledge in a transfer task. Finally, condition effects were moderated my children’s working memory and prior math knowledge.