Ulcerative colitis includes gastrointestinal and, in some cases, extraintestinal symptoms, potentially affecting any organ. Diagnosing such extraintestinal involvement can be challenging, especially when considering alternative aetiologies, including drug-induced toxicity. We report the case of an octogenarian male recently diagnosed with ulcerative colitis and undergoing treatment with mesalazine who was diagnosed with non-specific interstitial pneumonia due to respiratory symptoms. Subsequently, he presented with mucocutaneous jaundice, prompting a comprehensive evaluation, including a liver biopsy, the results of which suggested drug-induced hepatotoxicity, with mesalazine identified as the most likely cause. The temporal sequence, hepatic histopathological findings and respiratory improvement following mesalazine withdrawal and corticosteroid therapy supported the diagnosis of pulmonary toxicity without the need for additional invasive tests. This case, together with a review of the literature on mesalazine toxicity, suggests that drug-induced lung and hepatotoxicity may be more common than previously thought, emphasising the need to consider these conditions in extraintestinal manifestations of inflammatory bowel disease.