This research examined the experiences of immigrant students and emergent bilinguals in mathematics. The purpose of these studies was to identify, describe, and understand some of the various factors that impact mathematics achievement and success for these student groups through qualitative case studies and quantitative analysis of the 2015 TIMSS achievement data. The levels of analysis and study were chosen to take both a micro- and macro-lens to the issues of immigrant students and emergent bilinguals.The results of the first two studies suggest that prior educational experiences influence preferences for teaching and learning for students who make a transition from one educational culture to another. Indicators of success were identified so that students could self-report and relate them to their current performance in mathematics. The studies also show that models of success that are normed for dominant student groups may not be accurate for non-dominant groups in mathematics. They explore the Discourses that immigrant students are socialized into through the learning of mathematics, as well as how institutional factors impact how students participate in mathematics. The third study continued evaluating indicators of success, but through the 2015 8th grade TIMSS assessment results in five countries: United States, Canada, Italy, Botswana, and the United Arab Emirates. Models of success were developed using hierarchical linear modelling to understand how indicators of success impact both immigrant students and emergent bilinguals in each of these countries. The models were compared and contrasted to begin to understand the challenges of broadly generalizing students within these two populations. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]