The purpose of this multiple case study was to identify the forms of science capital that six groups of adolescents mobilized toward the realization of their self-selected engineering projects during after-school meetings. Research participants were high school students who self-identified as Hispanic, Latina, or Latino; who had received English as a Second Language (ESL) services; and whose parents or guardians had immigrated to the United States and held working class jobs. The research team used categories from Bourdieusian theories of capital to identify the forms of science capital mobilized by the participants. Data sources included transcripts from monthly interviews and from bi-monthly group meetings during which the group members worked on their engineering projects. Data analysis indicated that the groups activated science capital in the following categories: "embodied capital" in the form of formal scientific knowledge, literacy practices, and experiences with solving everyday problems; "social capital" in the form of connections with authorities, experts, and peers; "objectified capital" in the form of information and communication technologies (ICTs) and measuring tools; and "institutional capital" in the form of awards and titles. The participants co-mobilized multiple forms of science capital to advance their engineering projects, and some instances of co-mobilization enabled the future activation of subsequent forms of science capital. Engineering, as a vehicle for learning science, provided the youth with opportunities to draw from diverse community resources and from multilingual literacy practices, recasting these resources and skills as forms of science capital, which were mobilized toward the attainment of other high-status forms of science capital.