Infection of mice with coxsackievirus B4 results within days in a severe acute necrotizing pancreatitis, which resolves completely within weeks. Gelatinase B or matrix metalloproteinase 9 (MMP-9) has previously been shown to be involved in several models of pancreatitis, but its role in virus-induced pancreatitis has never been investigated. We here report that MMP-9 levels are markedly increased in the pancreas of mice that developed acute pancreatitis following infection with coxsackievirus B4. Moreover, using in situ zymography, we demonstrated that MMP-9 is active in vivo. Double immunohistochemical analysis revealed that macrophages and neutrophils were the cellular source of MMP-9. Extensive tissue rearrangements involving collagen turnover were observed, and these were associated with extensive pathology and resolution of the disease. In summary, this report demonstrates that acute coxsackievirus B4-induced pancreatitis involves the action of MMP-9, which is mainly originating from macrophages and neutrophils.