The need to increase students interested in pursuing careers in science, technology, engineering, and mathematics (STEM) is growing. The current study delivers results of an Upward Bound program focused on advancing students' interest toward STEM fields and careers. Project STEMulate, funded by the National Science Foundation's ITEST program, used Problem-Based Learning (PBL) in challenging students to engage in solving hands-on, real-world authentic problems in their communities. Project STEMulate takes structured PBL one step further by collaborating with local STEM Industry Partners for contextual learning and STEM pipeline development. The results revealed a raised interest in STEM, and a correlation between: 1) students' career interest and their science ability and motivation, and 2) their Science Self-Efficacy and PBL ratings associated with their interest in STEM careers. These results highlight the significant potential of PBL instructional strategies to increase students' attitudes toward and interest in future STEM careers.