A 76-year-old man with histopathologically proven prostate cancer (initial prostate-specific antigen 110 ng/mL, Gleason 3 + 4 = 7) received 18F-DCFPyL PET/CT for initial staging. Both the primary tumor and pathologically enlarged pelvic lymph nodes showed no increased 18F-DCFPyL uptake. Subsequent histopathologic lymph node biopsy revealed prostate cancer metastasis. Prostate-specific membrane antigen tracers, such as 18F-DCFPyL, are promising radiopharmaceuticals for prostate cancer imaging. False-negative prostate-specific membrane antigen PET/CT findings have been reported earlier for prostate tumors with neuroendocrine differentiation. However, this report presents false-negative 18F-DCFPyL PET findings of an adenocarcinoma of the prostate without neuroendocrine differentiation.