B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a common lymphoproliferative disorder with an increased risk of developing subsequent neoplasms of epithelial and mesenchymal origin. The decreased immunity and B-cell dysfunction in CLL probably accounts for this emergence of second malignancies. We report a case of synchronous bladder transitional cell carcinoma (TCC) and prostatic carcinoma with CLL. A 74-year-old male who underwent transurethral resection of the prostate (TURP) for benign prostatic hyperplasia 2 years before, presented with recurrent urinary tract infection. Peripheral blood smear revealed leukocytosis with absolute lymphocytosis (absolute lymphocyte count: 37870 cells/mm3). Flow cytometric immunophenotyping revealed 75% abnormal lymphoid cells which were positive for CD 19, CD5, CD23, CD22, CD200, CD20 (moderate) with lambda light chain restriction and negative for CD3, CD10, FMC7, CD38, CD138, IgM, CD103, CD123. 18 F Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) showed increased metabolic activity of the left lateral wall of the urinary bladder extending to the left UV junction, adjacent part of trigone and bladder neck region along with multiple heterogeneous enhancing areas with increased FDG avidity within the prostate. Transurethral resection of the bladder tumour by cystoscopy was performed. Histopathology showed high grade, muscle invasive urothelial carcinoma. Due to presence of uptake in the prostate, transurethral resection of the prostate was done and histopathology revealed adenocarcinoma of prostate (prostate specific antigen-positive), Gleason grade III+III and Gleason score 6. A high index of suspicion is required to detect synchronous and metachronous malignancies. Ancillary studies such as immunohistochemistry, flow cytometry and PET/CT are often essential for detection and an accurate diagnosis.