The researchers tested a model of the structural relationship between Black student engagement in out-of-school time (OST) science enrichment and participation in advanced science courses in high school. The participants in the sample were Black students (N = 3,173) who participated in the High School Longitudinal Study of 2009/2012. The student participants were in the ninth grade and ranged in age from 14 to 16 years. The results suggested that the model adequately fit the data, and that a direct relationship existed between OST enrichment and Black student participation in advanced science. In addition, Black female students participated statistically significantly more in advanced science than their male peers. Socioeconomic status also was a statistically significant indicator of advanced science course participation. Engagement in OST was not statistically significantly influenced by gender or socioeconomic status. This research extends the implications of informal science, technology, engineering, and mathematics (STEM) to support the diversification of advanced high school science courses and STEM participation by providing distinct estimates of the effects of OST on Black students.