There is a heated debate about the efficacy of growth mindsets in predicting achievement and other key learning-related outcomes with some studies supporting and others failing to find evidence of growth mindset's adaptive effects. Moreover, past studies on mindsets have mostly examined it as a psychological variable with little attention to how it interacts with socioeconomic status (SES). This study aims to examine (1) how growth mindsets are associated with key learning-related outcomes (i.e., motivation, engagement, and achievement) and (2) how growth mindsets interact with structural factors, specifically socioeconomic status at the individual and school level, in predicting key learning-related outcomes. The sample was drawn from the nationally representative Educational Longitudinal Study (ELS) dataset which contained responses from 15,362 tenth-grade students in the United States. Data were analyzed using hierarchical linear modeling to take into account the multi-level nature of the data. Though having a growth mindset was positively associated with better motivation and engagement for students across all socioeconomic strata, its effects on achievement were moderated by SES. A growth mindset positively predicted achievement only among students from more advantaged families but not among those from less advantaged families. This study highlights the importance of examining the interplay between mindsets and socioeconomic factors in understanding students' motivation, engagement, and achievement.