Cancer among adolescents and young adults (AYAs) has been a growing public health concern in France since 2009, a priority reaffirmed in the new 2026-2030 roadmap of the Ten-Year Cancer Control Strategy. This issue is also generating increasing interest internationally, as evidenced by the emergence of scientific conferences dedicated to this population. However, the socioeconomic inequalities associated with cancer mortality among AYAs remain insufficiently documented internationally. The objective of this study is to analyze the socioeconomic determinants associated with cancer mortality among AYAs. Epidemiological data on cancer patients aged 15 to 39 are available for 37 countries for 2000 to 2023, these data being drawn from the Global Burden of Disease (GBD 2023) databases. For this study, they were supplemented by socioeconomic indicators from the United Nations Development Program and the World Bank. Descriptive analyses, correlations, principal component analysis, classification methods, time-series trend analyses (EAPC and Joinpoint), and panel data models have been performed. Results highlight a strong socioeconomic gradient in mortality. High-income countries have an average standardized mortality rate of 1.5 per 100,000 inhabitants, compared to 3.7 per 100,000 inhabitants in lower-middle-income countries. The mortality-to-incidence ratio decreases from 0.45 to 0.15 with increasing income level. Multivariate analyses confirm a significant association between the Human Development Index and cancer mortality among adolescents and young adults (AYAs), after adjusting for other model variables. Joinpoint analyses also reveal heterogeneous temporal trends according to sex and cancer type. This study highlights importance of socio-economic determinants in international inequalities in cancer mortality among AYAs.