This study explored the role of growth in the executive components of working memory (WM) on second language (L2) mathematical problem-solving in elementary school children who are emerging bilinguals whose first language (L1) is Spanish. To this end, children (N = 429) in Grades 1, 2, and 3 at Wave 1 were administered a battery of math, reading, vocabulary, and cognitive (short-term memory [STM], working memory [WM], rapid naming, and inhibition) measures. The battery of tests was administered again 1 year and 2 years later to the same participants. Four important findings emerged: (a) growth in the executive of WM was significantly related to growth in L2 math problem-solving independent of growth in reading, vocabulary, fluid intelligence, inhibition, and rapid naming speed; (b) a Nonmath achievement/aptitude (i.e., reading, vocabulary) model provided a better fit to the data than domain-specific math and process models; (c) the relationship between WM and L2 math problem-solving was significantly mediated by L1 mathematical problem-solving and English vocabulary; and (d) the influence of WM on L2 math problem-solving was unidirectional. Taken together, this is the first comprehensive study of the link between growth in WM and growth in emerging bilingual children's mathematical problem-solving in 2 language systems. The results are discussed within the context of four models that assess the contribution of WM in predictions of later math problem-solving in emergent bilingual children.