The most popular hypothesis circulating within and beyond the scientific community is that viral infections enhance or elicit autoimmune disorders such as type 1 diabetes. Indeed, viruses can injure β-cells and have been isolated in pancreatic tissues from diabetic patients. However, accumulating evidence suggests that the opposite scenario, which is prevention or amelioration of type 1 diabetes, might be at least as common an outcome of viral infection. Here, we discuss epidemiological and experimental evidence for the main mechanisms accounting for the role of viruses in type 1 diabetes to better understand the complex relationship between viral infections and autoimmune diabetes.