We present a unique case of a sarcoma arising in a testicular non-seminomatous mixed germ cell tumour with a predominant yolk sac tumour (YST) component. This is the first case reported in which a sarcoma is linked to YST of the testis in a patient not having undergone prior chemotherapy. This finding confirms the ability of YST to contain sarcoma; it underlies its importance for urologists, oncologists and pathologists to be aware of this phenomenon and to modify treatment strategies appropriately.