Gastric Crohn's disease is a rare manifestation of Crohn's disease affecting the stomach, unlike its more common forms that primarily affect the ileum and colon. This is a case of an 18-year-old female who was referred to gastroenterology for investigation of iron deficiency anaemia, which was first noted when she was 15 years old. Investigation for persistent iron deficiency anaemia (IDA) revealed high faecal calprotectin and a positive faecal immunochemical test (FIT). Endoscopy was done, which revealed mild haemorrhagic gastritis and a few superficial gastric erosions. Biopsies taken from the gastric fundus indicated ill-defined granulomas with no significant active inflammation and no presence of Helicobacter pylori. Colonoscopy done up to the caecum was normal endoscopically. However, the random colonic biopsies taken from the ascending colon revealed mild active chronic inflammation. Granulomas were seen, in keeping with Crohn's colitis, making this a case of gastric Crohn's disease with ileocolonic involvement. The patient was treated with budesonide for acute symptom management. Following discussion in the inflammatory bowel disease (IBD) multi-disciplinary team meeting (MDT), she was commenced on Infliximab. Follow-up evaluations showed no significant relapse episodes. This case also highlights the importance of family history and genetic evaluation in patients with potential hereditary or autoinflammatory conditions, which would aid in narrowing the diagnostic spectrum.