To understand mathematics, children must interpret mathematics symbols. In this study, we designed a brief assessment of mathematics symbols for children in the elementary grades. For each of 23 symbols, children identified the symbol, provided the meaning of the symbol, and used the symbol. We assessed 297 children in Grades 1, 3, and 5. Internal consistency reliability was established across grade levels. Results indicated the overall symbol knowledge of children increased across grade levels, and children demonstrated higher scores on questions related to the identification and use of the symbol rather than explaining the meaning of the symbol. Across grades, symbol knowledge was a significant predictor of mathematics computation, although the variance accounted for was greatest in first grade and least in fifth grade.