Introduction: Grandparents are often highly involved as secondary caregivers for their grandchildren and may influence children's psychological and physical health outcomes. The purpose of the current review was to gather and synthesize research findings on the effects of grandparent involvement on children's physical health outcomes. Method: PubMed, PsycInfo, and MedLine were searched by 3 independent reviewers for articles that reported on grandparent involvement and children's health. Twenty-six articles were included for final review based on selection criteria. Results: Relatively few studies have examined the effects of grandparent involvement on children's health outcomes; therefore, the degree of their influence remains unclear. Four categories of children's health outcomes (disease/illness, weight, eating behaviors, and injury/safety) emerged during this review. Results indicated that the majority of studies available reported a negative effect of grandparent involvement on child's weight status. However, it is important to note that in most of these studies, the effects of grandparent involvement were not a primary outcome, and the amount of time grandparents spent with their grandchildren was not accounted for. Many studies in this review were qualitative studies, limiting the types of analyses that could be conducted. In addition, few longitudinal studies have been conducted in this area. Discussion: Based on this review, it is clear that grandparents are involved in caretaking for children across many cultures but to understand their role in children's health outcomes, more systematic and longitudinal research needs to be conducted.