The purpose of the current study was to examine four family context variables (socioeconomic status, mother's level of education, father's level of education, and perceived family social support) as predictors of math self-concept among undergraduate STEM majors to better understand the gender differential in math self-concept. Participants included 499 undergraduates (75% of whom were female) at a large research university in the southwestern United States. Results indicated that males had higher math self-concepts than females and that social support predicted math self-concept, particularly for males. (Contains 2 tables and 2 figures.)