Background: This realist review was conducted to understand how stigma is reduced in relation to HIV test uptake in low- and middle-income countries (LMICs). Methods: A systematic search of eight databases resulted in 34 articles considered for synthesis. Data synthesis was guided by a preliminary programme theory and included coding the meaning units to develop themes or intervention pathways that corresponded to context-mechanism-outcome configurations. Results: We found that the interventions produced an effect through two pathways: (a) knowledge leads to changes in stigmatizing attitudes and increases in HIV test uptake and (b) knowledge and attitudes lead to changes in stigmatizing behaviours and lead to HIV test uptake. We also found one competing pathway that illustrated the direct impact of knowledge on HIV test uptake without changing stigmatizing attitudes and behaviour. The identified pathways were found to be influenced by some structural factors (e.g., anti-homosexuality laws, country-specific HIV testing programmes and policies), community factors (e.g., traditional beliefs and practices, sexual taboos and prevalence of intimate partner violence) and target-population characteristics (e.g., age, income and urban-rural residence). Conclusions: The pathways and underlying mechanisms support the adaptation of intervention strategies in terms of social context and the target population in LMICs.