We report the case of a 76-year-old patient with a past medical history of low-grade chronic lymphocytic leukaemia who presented with severe chronic bladder symptoms attributed to interstitial cystitis. She underwent cystectomy and ileal conduit formation after the failure of all conventional treatment. Bladder histopathology revealed primary splenic marginal zone lymphoma. Literature review shows the rarity of such non-hematopoietic visceral metastases. This may represent the first reported splenic marginal zone lymphoma with bladder involvement and highlights the clinical and histological similarities with interstitial cystitis.