Using data from the Program for International Student Assessment (PISA), the size of the literacy achievement gap between 15-year-old students from two-parent and those from single-mother households were compared across 18 industrialized nations. This study found that cross-national differences exist in the association between single motherhood and literacy achievement. The research findings also indicate that economic deprivation and parental involvement moderate the association between family structure and student literacy achievement. (Contains 7 tables.)