In most cases, prostate cancer spreads locally to the seminal vesicles, via lymphatics to pelvic and abdominal lymph nodes, and hematogenously to the bones. Direct invasion along nerve roots is exceptionally rare but can occur. Here, we present a case with 18 F-DCFPyL PET/CT images showing neoplastic involvement of the lumbosacral plexus in a patient with recurrent prostate cancer.