Of pancreatic pseudocysts, approximately 30% are complicated by abscess formation, perforation into the abdominal cavity, penetration to the gastrointestinal tract, or bleeding. We report two cases of pancreatic abscess complicating severe acute pancreatitis in which the abscess penetrated to the gastrointestinal tract during the course of treatment with endoscopic ultrasound (EUS)-guided pseudocyst drainage. In these cases, neither aggravation nor recurrence of the pancreatic abscess has been identified since the event occurred. The EUS-guided treatment was effective for improvement of severe inflammation of the pseudocyst as an initial treatment. However, drainage tube placement limitations pertained because the pseudocyst was present with multilocular infection. Penetrations eventually contributed to their resolution because the fistulas were used as wide drainage routes. It is important to understand the courses of these cases for preparation of therapeutic strategies to treat pancreatic pseudocyst/abscess.