The American educational system currently yields disappointing levels of science, technology, engineering, and math (STEM) engagement and achievement among students. One way to remedy this may be to increase children’s motivation in STEM from an early age. This study examined whether a social cue—being part of an experimental “minimal group”—increases STEM engagement in preschoolers (N = 141; 4.5-year-olds). Using a within-subjects design, participants were assigned to a group and an individual condition (counterbalanced for order) before they worked on a math task and a spatial task. Children persisted longer on, placed more pieces correctly, reported higher self-efficacy, and were more interested in the group STEM task than the individual STEM task. In addition, we conducted a continuously cumulating meta-analysis (CCMA) to combine the results of the current experiment with two previous experiments. These findings suggest that incorporating nonacademic social factors, such as group membership, into current STEM curricula could be an effective way to boost young children’s STEM motivation.