This article reports an uncommon cause of gastrointestinal bleeding in a young male with uncorrected Tetralogy of Fallot (TOF). This is the first reported instance of gastrointestinal stromal tumor (GIST) causing bleeding in a patient with uncorrected TOF. A 32-year-old Caucasian male with severe developmental delay and uncorrected TOF presented with black tarry stools. On admission, the patient was hypotensive and tachycardic. He was successfully resuscitated with fluids and blood transfusion. Upper gastrointestinal endoscopy was performed and biopsy revealed GIST. It is interesting to note that the patient survived till this age without any medical or surgical treatment. This case presents GIST as a cause of gastrointestinal bleeding in uncorrected TOF. Cytogenetic analysis revealed deletion of short arm of chromosome 18. This case illustrates that tyrosine kinase inhibitor may be an acceptable alternative therapy to surgical resection.