Data from a longitudinal investigation were used to examine the effects of mothers' and teachers' language on children's developing mathematical competencies during the kindergarten year. Specifically, 1) mothers' use of metamemory talk, or references to the process of remembering, and 2) teachers' use of "cognitive processing language" (CPL), or instruction that encourages deep levels of processing and metacognition, were related to students' addition skills in kindergarten. The findings indicated that while maternal metamemory talk was associated with children's mathematical competencies at school entry, teachers' use of CPL was associated with the amount of growth that students demonstrated across the year, especially regarding strategy use. The results highlight the need for additional research that examines students' academic trajectories longitudinally as a function of the language to which they are exposed at home and school.