Oral 5-aminosalicylic acid (5-ASA) are well recognised to have the potential to cause drug-induced acute pancreatitis; however, there have only been infrequent case reports of rectal formulations causing acute pancreatitis. We describe a case of rectal Mesalazine (a 5-ASA) induced acute pancreatitis. The patient was commenced on rectal 5-ASA therapy 8 weeks prior to presentation following a diagnosis of Montreal classification E1 Ulcerative Colitis on colonoscopy. After the diagnosis of acute pancreatitis was confirmed, 5-ASA was ceased and the patient made a clinical full recovery at 2 month follow-up. Despite its reduced systemic absorption, rectal 5-ASA like oral formations must be considered as a potential trigger for acute pancreatitis in patients with inflammatory bowel disease.