The Wilms tumour is the fourth most common paediatric malignancy. On the contrary, it is extremely rare in adults as it accounts for less than 1% of all renal malignancies. This scarcity of cases placed a significant challenge in generating evidence-based treatment. Hence, treatment of adult Wilms considerably varies between centres. Standardised guidelines based on international expert consensus for adults have been introduced to help steer management. However, reporting patient outcomes remains limited. In this article, a case study will be presented. This includes modalities of treatment, side effects, tolerability, and outcome. A 40-year-old gentleman with histology consistent with the Wilms tumour received adjuvant chemotherapy according to the UMBRELLA SIOP2016 adult guidelines. Such guidelines were originally adapted from the International Society of Paediatric Oncology protocol. The patient underwent eight cycles of vincristine, actinomycin-D, and doxorubicin and concurrent radiation therapy. Use of the UMBRELLA SIOP2016 adult guideline was shown effective at treating the Wilms tumour in this adult case with minimal severe toxicity. Ongoing follow-up is still needed to determine the long-term effects and prognosis of the patient.