Which occupation to pursue is one of the more consequential decisions people make and represents a key developmental task. Yet the underlying developmental processes associated with either individual or group differences in occupational choices are still not well understood. This study contributes toward filling this gap, focusing in particular on the math domain. We examined two aspects of Eccles et al.’s (1983) expectancy–value theory of achievement-related behaviors: (a) the reciprocal associations between adolescents’ expectancy and subjective task value beliefs and adolescents’ career plans and (b) the multiplicative association between expectancies and values in predicting occupational outcomes in the math domain. Our analyses indicate that adolescents’ expectancy and subjective task value beliefs about math and their math- or science-related career plans reported at the beginning and end of high school predict each other over time, with the exception of intrinsic interest in math. Furthermore, multiplicative associations between adolescents’ expectancy and subjective task value beliefs about math predict math-related career attainment approximately 15 years after graduation from high school. Gender differences emerged regarding career-related beliefs and career attainment, with male students being more likely than female to both pursue and attain math-related careers. These gender differences could not be explained by differences in beliefs about math as an academic subject.