The purpose of this qualitative study was: (a) to explore the cognitive and metacognitive processes of mathematics problem-solving discourse of 10-year-old students in Russia, Spain, Hungary, and the United States; and (b) to explore the patterns of social interactions during small group work. Data were analyzed using a cognitive/metacognitive framework adopted from Artzt and Armour-Thomas. The analysis of think-aloud transcripts, students' reflective journals, and field observation notes revealed similar patterns of cognitive/metacognitive processes of the problem-solving discourse at the four research sites and distinct patterns of social interactions. Implications of how children used metacognition to impact learning during mathematics problem solving are discussed.