OBJECTIVE To employ enzyme-linked immunosorbent assay (ELISA) to measure the serum level of thrombospondin-1 (TSP-1) and analyze its diagnostic value for prostate cancer. METHODS The serum levels of TSP-1 were measured by human TSP-1 ELISA kit in 50 patients with organ-confined prostate cancer (n = 22) and non-organ-confined prostate cancer (n = 28). And the subjects of benign prostatic hyperplasia (BPH, n = 20) and healthy controls (n = 16) were selected. RESULTS The average serum concentration of TSP-1 was (200 ± 49) µg/L in prostate cancer group, (281 ± 53) µg/L in BPH group and (323 ± 56) µg/L in healthy control group. There were significant inter-group differences in the serum levels of TSP-1 (both P < 0.05). The average serum concentration of TSP-1 was (216 ± 34) µg/L in organ-confined prostate cancer (including stages I and II) and (188 ± 49) µg/L in non-organ-confined prostate cancer (including stages III and IV) respectively (P = 0.030). The level of TSP-1 was also correlated with Gleason score (r = -0.32, P = 0.023). However, the relationship between TSP-1 levels and lymph node metastasis remained elusive (P = 0.189). The diagnostic sensitivity and specificity of TSP-1 and prostate specific antigen (PSA) for prostate cancer were 72%, 90% and 64%, 70% respectively (both P < 0.05). The area under the receiver operating characteristic curve (ROC) of TSP-1 and PSA were 0.886 and 0.719 respectively (P = 0.028). CONCLUSION As a relatively ideal predictor of prostate cancer, the serum concentration of TSP-1 can not only distinguish prostate cancer from BPH, but also correlate with tumor stage and Gleason grade.