Externalization theory assumes that risks and costs are systematically displaced from high-income countries (HICs) to low- and middle-income countries (LMICs). We review how and why transnational tobacco companies (TTCs) influence the local circumstances of LMICs that trigger externalization mechanisms, leading to tobacco-attributable risk outcomes. Our realist synthesis of scientific evidence and gray literature identifies externalization mechanisms with risk outcomes at the level of health policy, smoking trends, and tobacco production. The results reveal the mediating role of local and global third parties and intermediaries. Externalization mechanisms produce systematic tobacco-attributable inequalities between places located in HICs and those located in LMICs.