This chapter reports on the social inequalities within countries in the Trends in International Mathematics and Science Study (TIMSS) 2019 environmental knowledge scale. The variation within countries on the distribution of environmental knowledge is reported, calculating the achievement gaps between sociodemographic groups—specifically, between low and high socioeconomic status students, between boys and girls, and between rural areas and urban areas. The results show high variation across countries and regions in the performance of their students. Results also reaffirm socioeconomic status as an important predictor of achievement, in this case in environmental knowledge, with all countries and regions presenting significant and relatively high gaps between low and high socioeconomic status students. In contrast, the gaps based on gender and urbanicity depended much more on the context of each country, being present in roughly half the countries and with different directions. These results reflect the pending challenges regarding how to tackle environmental crises from a global perspective.