As global economic uncertainties increasingly constrain opportunities for young populations, understanding the interplay between internal psychological resilience and external economic reality is vital for promoting positive youth development. Anchored in Social Cognitive Theory and Grit Theory, this study investigated the relationships among perceived agency, grit, and thriving among youths facing economic adversity, with specific attention to the moderating role of socioeconomic status (SES). A quantitative cross-sectional survey design was employed, sampling 277 youths (ages 18–35) within Kaduna Metropolis, Nigeria. Data were collected using the General Self-Efficacy Scale, the Short Grit Scale, the Brief Inventory of Thriving, and a composite SES index. Bivariate correlations revealed that perceived agency (r = .46) and grit (r = .52) were significantly and positively associated with thriving, as was SES (r = .40). Hierarchical moderated multiple regression analyses confirmed that SES significantly moderated both the relationship between perceived agency and thriving (ΔR² = .028, p = .009) and the relationship between grit and thriving (ΔR² = .033, p = .002). The positive associations between perceived agency, grit, and youth thriving were significantly stronger under conditions of higher socioeconomic advantage. These findings highlight a critical boundary condition for psychological interventions, suggesting that efforts to build individual resilience must be coupled with systemic socioeconomic support to effectively foster positive mental health in high-stress, resource-scarce environments.