Stress granule (SG) formation is a primary mechanism through which gene expression is rapidly modulated when the eukaryotic cells undergo cellular stresses (including heat shock, oxidative stress, starvation, viral infection). SGs have been proposed to affect mRNA translation and stability, as well as being linked to apoptosis and nuclear processes. Formation of SGs after viral infection result in blockade of viral protein synthesis and viral replication. Not surprisingly, viruses from diverse families have been found to modulate SG formation in infected cells by associating with important SG effector proteins. Here we provide a summary of the current understanding of the mechanism of SG formation, describe the current knowledge on viruses induce and/or modulate SGs in infected cells via phosphorylation of eIF2α, and regulation of SGs in virus systems. Further, we summarize recent progresses in understanding the relationship between viruses and stress granules in mammalian cells, and suggest that SG formation is an important aspect of the antiviral innate immune response.