Project-based science (PBS) curricula have project- and inquiry-based aspects that leverage the strengths of urban students from ethnic and racial groups underrepresented in science careers, potentially impacting positively these students' science achievement and attitudes and thus their college and career plans. We aimed to determine the extent to which a PBS curriculum would show this. We provided professional development to bolster urban teachers' science content knowledge (CK) and science pedagogical content knowledge (PCK) to observe the maximal impact of the PBS curriculum. We found that students' science achievement improved with the PBS curriculum, but that their attitudes toward science and plans to pursue science did not. Increases in teachers' CK and PCK with the professional development correlated with the improvements in student science achievement but did not correlate with improvements in student science attitudes or plans. However, the frequency of teachers' use of specific inquiry-based activities did correlate with improvements in students' science attitudes and plans. In sum, the extent of the success of a PBS curriculum with students from groups underrepresented in science careers appears to be dependent on elements of both teacher knowledge (CK and PCK) and teachers' frequency of use of inquiry-based activities that are consistent with culturally relevant pedagogical practices. (Contains 8 tables.)