Abstract: Prostate cancer (PCa) is one of the common malignant tumors of the genitourinary system in men. It is generally believed that the serum prostate-specific antigen (PSA) level exceeding 4.0 ng/mL has potential diagnostic value for PCa. However, there are many cases of PCa with low PSA levels in clinical practice, specifically between 0-4.0 ng/mL. These cases may be missed or even misdiagnosed due to low PSA levels, leading to delays in treatment and missing the optimal clinical window for diagnosis and treatment. This review provides a comprehensive summary of the clinicopathological characteristics of PCa patients with PSA levels below 4.0 ng/mL, including their baseline and clinical features, histological characteristics, imaging features, neuroendocrine prostate cancer (NEPC) and prognostic factors, aiming to enhance the understanding of this type of PCa.