Introduction: Individuals' math value beliefs are theorized to influence who persists in STEM. However, the existing findings on gender differences in adolescents' math value beliefs are inconsistent. The goal of this study was to use three existing datasets to help clarify when gender differences emerge for high school adolescents and for whom (i.e., adolescents across historical time, grade level, and race/ethnicity). Specifically, we examined the extent to which gender differences in adolescents' math value beliefs (i.e., interest, utility, and attainment) replicated (1) across three datasets spanning the 1990s to 2010s, (2) from 9th-12th grade, and (3) within each of the four largest U.S. racial/ethnic groups (i.e., Asian, Black, Latine, and White adolescents). Methods: We tested these aims with three existing longitudinal U.S. datasets: the California Achievement Motivation Project (CAMP) (n = 8855), the Childhood and Beyond Study (CAB) (n = 582), and the High School Longitudinal Study (HSLS) (n = 21,000). Students were in high school (9th-12th grade) and half were girls (49%-53%). All three datasets included measures with the same or similar math value belief items, making conceptual replication possible. Results and Conclusions: Overall, we did not find strong evidence for meaningful gender differences in adolescents' math value beliefs overall. We did find meaningful gender differences in the oldest data set (CAB). When examined within each racial/ethnic group, we found no evidence of gender differences in math value beliefs among Black or Latine adolescents, but some differences among Asian and White adolescents. The findings align with the gender similarities hypothesis, suggesting adolescent girls and boys had similar math value beliefs.