Students’ socioeconomic status (SES) is not only directly related to mathematics achievement but also indirectly related to mathematics achievement through their unequal opportunity to learn (OTL). Despite a plethora of studies about how mathematics achievement is associated with SES and OTL, few systematic studies have examined the differential role SES plays in the relationship between curriculum-based mathematics performance and application-based mathematics literacy. To bridge the gap in the literature, this study aims at addressing the relationship between curriculum-based mathematics and application-based mathematics while considering the OTL associated with students at the two different assessment time points. Using the unique data set from the Russian Federation in which a subset of the 2011 Trends in International Mathematics and Science Study (TIMSS) student sample also took the Program for International Student Assessment (PISA) assessment 1 year later, we found that lower SES students had difficulties in transferring their curriculum-based mathematics knowledge and skills to mathematics literacy, which plays an important role in the present society’s high-complexity demands. These results suggest that students with a lower SES need to receive greater attention and focus on their mathematics learning so as to improve their capacity to interpret and evaluate real-world problems mathematically and to make better decisions using this competency.