The decreasing number of young students pursuing science careers has become a rising concern worldwide, particularly in China. Educational programs with empirical evidence of promoting young students' pursuit of science careers are still lacking. Here, drawing on the existing literature, we designed and implemented a 3-day quasi-apprenticeship program in a research botanical garden of China. We used a pre-post test design, with hypotheses based on the Theory of Planned Behavior and provided both quantitative and qualitative data to evaluate the efficacy of the program on 319 seventh- and eighth-grade Chinese students from 15 public schools. The quantitative findings by using generalized estimating equations indicated that students' attitudes, subjective norms, science self-efficacy, and career intention were significantly enhanced after the program; the structural equation modeling result showed that the enhancement of career intention could be explained by increases in subjective norms and science self-efficacy. The qualitative findings also supported the notion that a high proportion of students mentioned gains in increased science self-efficacy from attending the program. We suggest a short-term program, engaging students in group work of authentic science practices with mentors in an authentic context, might be a cost-effective strategy for supporting Chinese young students' pursuit of science careers. This study also provides valuable information, through both pedagogical and theoretical structure elements, for educators and researchers who design, deliver, and evaluate educational programs to promote secondary school students' pursuit of science careers.