<p>Inflammatory bowel disease (IBD) is associated with extraintestinal cardiovascular effects. While tachycardia is common during active inflammation, bradycardia is exceptionally rare. We report a case of transient sinus bradycardia occurring during an acute severe ulcerative colitis flare in which no alternative cause was identified after structured evaluation. A 23-year-old Syrian woman with severe, long-standing ulcerative colitis (pancolitis) was hospitalized during an intense flare, with over ten daily bloody bowel movements, pain, and nighttime bleeding. Despite ongoing treatment with mesalamine, azathioprine, and intensified infliximab, her inflammatory markers were elevated. On day three, she developed transient dizziness. Unexpectedly, her heart rate slowed significantly (sinus bradycardia), which is a rarity in IBD, where fast heart rates are more common. A structured cardiac evaluation did not identify myocardial injury, electrolyte disturbance, thyroid dysfunction, or infection, and no temporal association with any medication was observed. The patient’s cardiac structure and function were normal. Crucially, the slow heart rate resolved spontaneously by day seven as her colitis improved with treatment, including an extra infliximab dose. This case suggests that severe intestinal inflammation may be accompanied by transient, reversible disturbances of heart rhythm, possibly through autonomic mechanisms; however, a causal relationship cannot be established from a single observation. Clinicians should nonetheless remain alert to unusual cardiac symptoms during IBD flares.</p>