We report 3 cases with unusual complications of gastric outlet obstruction caused by a gastrostomy tube balloon. All cases developed vomiting, and 2 cases were accompanied by hematemesis. Gastric ulcer was observed in 1 case, aspiration pneumonia was observed in 2 cases, and pancreatitis was observed in 1 case. This condition improved rapidly by correction of the position of the balloon in all cases. In patient vomiting during management for gastrostomy we need to consider migration of the gastrostomy tube balloon. Careful management of the gastrostomy tube balloon is important.