Rupture into the portal vein is a rare complication of a pancreatic pseudocyst. Only 15 cases of such an incidence have been described in the literature. Only one of these was diagnosed with magnetic resonance imaging (MRI), the rest being diagnosed using other invasive diagnostic modalities or at surgery. We report a case of this rare complication diagnosed on MRI and also describe the demonstration of residual lysed thrombus within the portal vein as a new feature on MRI which supports this diagnosis. The presence of liver necrosis present in our case is a probable effect of this complication not described in the literature before. Early diagnosis of this potentially lethal complication can help in the proper management of these patients.