This study investigates how emotional attachment between a child and a custodial parent influences heritage language (HL) retention in single-parent migrant households. Using PRISMA guidelines, we identified 835 studies through database searches in Scopus and Google Scholar. After removing 152 duplicates and screening 683 full texts, 18 studies met the inclusion criteria for qualitative synthesis. Findings reveal that warm, affirming emotional bonds and consistent HL use by parents, especially mothers, support stronger language retention. However, only one study focused on single-parent families, and few employed quantitative methods, highlighting a critical research gap at the intersection of emotional dynamics and HL maintenance. We aimed to makes three key contributions: (1) the first systematic review to examine emotional attachment as a central variable in heritage language retention within single-parent households, (2) identify a significant research gap, with only one study directly focusing on single-parent contexts, and (3) propose a multidimensional conceptual framework linking emotional bonds, parental practices, and child agency to HL outcomes.