This paper reviews 10 years of research on virtual manipulatives (VMs) in K-5 mathematics education with a focus on moving beyond generalized conclusions that VMs can support learning to better understanding how and when they support learning. Synthesis of fifteen articles that met the inclusion criteria revealed researchers are beginning to unpack how particular features of VMs and context variables interact with student learning outcomes. The influence of context variables, such as whether VMs are used by individual students or used collaboratively, suggests a need for greater attention to the role of the teacher in implementation of VMs. Attention to the teacher's role in defining how VMs are used could inform future directions for teacher education.