Collagenous gastritis is a rare gastrointestinal disorder characterized in pediatrics by abdominal pain and anemia. The literature divides collagenous gastritis into distinct pediatric-onset and adult-onset phenotypes. As opposed to pediatric form, the adult form is associated with collagenous colitis and presents clinically with voluminous non-bloody diarrhea. There are over 25 case reports of collagenous gastritis of which 10 are pediatric cases. We present two cases of pediatric onset collagenous gastritis: one with a classic pediatric presentation, the other with findings typical of adult-onset disease. This is the first report of the adult-onset phenotype collagenous gastritis in a pediatric patient.