BACKGROUND: Non-pigmented tumours of the iris are rare and their clinical classification can be difficult, especially in the absence of systemic manifestations. HISTORY AND SIGNS: We report the case of a unilateral vascular, non-pigmented iris tumour in a 47-year-old patient. Clinically, the iris lesion showed progressive growth and tumour vascularisation. THERAPY AND OUTCOME: A systemic work-up failed to reveal any underlying systemic disease. Biopsy showed a non-necrotising granuloma. The lesion responded well to systemic corticosteroid therapy. CONCLUSIONS: Isolated granulomas of the iris are rare and clinically often indistinguishable from malignant tumours like melanoma. Due to the clinical course and the regression under corticosteroid therapy we concluded that this iris granuloma may be an isolated ocular manifestation of sarcoidosis.