In this qualitative study, we assessed the impact of the NE STEM 4U intervention on elementary school youth in terms of excitement, curiosity, and STEM concepts. The NE STEM 4U intervention incorporates a problem-based learning theoretical framework in an after-school time, weekly or twice-weekly intervention. We assessed student performance over two academic years of participation in the intervention using the Dimensions of Success observational tool. Ultimately, we link this mentor-led program with increases in curiosity, inquiry, and STEM concept gains. Taken together, these findings support after-school interventions in STEM areas as key encouraging excitement in youth and motivation to pursue a career in a STEM content area.