In the present study, we investigated whether parents’ beliefs about their high school aged adolescents’ spatial abilities (i.e., spatial visualization, mental manipulation, and navigation abilities) differed based on their child’s gender. We also examined whether these beliefs related to parents’ encouragement of their child to pursue a Science, Technology, Engineering, or Mathematics (STEM) career as well as students’ actual STEM major and career intentions. Data were collected from 117 pairs of U.S. high school students and one of their parents. We found that parents of young men thought their child had higher mental manipulation and navigation abilities than did parents of young women, even after statistically controlling for adolescents’ actual spatial abilities. Parents who perceived that their child had higher mental manipulation ability were more likely to encourage their child to pursue a STEM career, and those students were more likely to report that they intended to pursue a STEM career. These findings suggest that parents’ beliefs about how good their child is at spatial tasks may be based more strongly on gender stereotypes than on their child’s actual spatial abilities. Helping to make parents aware of these beliefs could be a potential lever of intervention to increase women’s participation in STEM careers.