The purpose of this study is to investigate environmental factors that affect mathematics learning of students in multicultural families. For this study, as study subjects, eight elementary school students and one middle school student, who were born and grew up in multicultural families in Korea due to international marriage of Korean father and foreign mother, and their five mothers were selected. To examine factors affecting mathematics learning and interests of students in multicultural families, relationships with parents, friends, and teachers were surveyed, and mathematics attitude test was performed. After conducting one on one interview based on collected questionnaires and results of the attitude test, qualitative data analysis was performed. As a result of survey and interview, positive factors affecting mathematics learning of students in multicultural families included arousing interest in mathematics through mother's mathematics teaching in her mother language and direct teaching, good peer relation, teacher's compliment and encouragement, and lowering the burden of language in accordance with characteristics of mathematics course.