Thesis advisor: Elida V. Laski / Strategy selection is an essential aspect of problem-solving, particularly within the domain of mathematics. This dissertation examines the mechanisms that guide children’s arithmetic strategy selection in order to advance theoretical understanding of this essential component of cognitive development. Better understanding of arithmetic strategy selection is important because individual differences in children’s arithmetic strategies are predictive of arithmetic accuracy and later math achievement. The current study builds upon prior research that has identified cognitive processes associated with strategy selection by considering the role of metacognitive judgments. The study investigated the direct and indirect effects of cognitive and metacognitive factors on strategy selection in a group of first and second grade students (n = 126). The majority of students generated metacognitive judgments of their competence using decomposition (an advanced strategy at this age) that were consistent with their actual ability. In these cases, their judgments of competence were related to the frequency with which they used decomposition strategies. Additionally, children’s metacognitive judgments of the anticipated amount effort required to execute decomposition mediated the association between children’s cognitive processes/pre-requisite knowledge (working memory and fact fluency) and the frequency with which they used it. Theoretical and practical implications of these findings are discussed. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Lynch School of Education. / Discipline: Counseling, Developmental and Educational Psychology.