The objective of this study is to assess the effectiveness of community health workers (CHWs) in Brazil. This systematic review included all studies that sought to assess interventions involving CHWs. Despite the low quality of evidence for most outcomes, analysis of the 23 publications included often found benefit for CHW intervention, best documented for frequency of child weighing, prevalence of breast-feeding, and delayed introduction of bottle-feeding. These findings and the current major role CHWs play in Brazil suggest that clarifying the benefit of CHW actions across a broad range of health care interventions should be a major research priority.