A 70-year-old man presented with left loin pain without urinary symptoms. Initial investigations with CT showed enlarged para-aortic, mediastinal lymph nodes, right-side renal mass and enlarged prostate. A prostatic-specific antigen (PSA) was alarmingly high at 4750 μg/L (normal <4.0 μg/L). Further investigations included positron emission tomography (PET); both prostate-specific membrane antigen and 18-fluorodeoxyglucose as well as bone scan and bone marrow examination confirmed dual malignancies with B-cell non-Hodgkin's lymphoma (B-NHL) and wide spread metastatic prostatic adenocarcinoma (PA) to the skull, spine, pelvis, liver and lungs. The patient was treated with six cycles of rituximab, etoposide, prednisone, vincristine, cyclophosphamide and doxorubicin(R-EPOCH) containing regimen for B-NHL and goserelin hormonal therapy for PA. Restaging with PET scans thereafter showed complete remission of NHL with disappearance of his metastatic PA and normalisation of PSA levels. R-EPOCH regimen and antiandrogen therapy resulted in a good outcome and remission of both malignancies.