Methods: Using the random-effects meta-analysis model, we investigated the effect of informal caregiving on all-cause mortality across 12 longitudinal population-based studies (seven United States; five international: United Kingdom, Northern Ireland , Japan, and Australia). Results: Across the studies, the combined effect of informal caregiving on all-cause mortality was 16% lower in favor of caregivers. Subgroup analyses revealed that the relationship between informal caregiving and all-cause mortality was not significant among the U.S. studies, in contrast to the international studies. Also, the mortality advantage of informal caregivers was not evident among those studies in which informal caregiving was operationalized precisely (Activity of Daily [ADL]/Instrumental Activity of Daily Living [IADL] assistance) as opposed to more broadly. Furthermore, studies in which the kinship tie between the informal caregiver and care recipient was unspecified tended to find a mortality advantage in favor of caregivers. Conclusions: When covariates were considered, the results of this meta-analysis provided more support for stress theory than the healthy caregiver hypothesis.