Prostate cancer is the most common malignant tumour in men. Improved testing for di- agnosis, risk prediction, and response to treatment would improve care. Here, we identified a pro- teomic signature of prostate cancer in peripheral blood using data-independent acquisition mass spectrometry combined with machine learning. A highly predictive signature was derived, which was associated with relevant pathways, including the coagulation, complement, and clotting cas- cades, as well as plasma lipoprotein particle remodeling. We further validated the identified bi- omarkers against a second cohort, identifying a panel of five key markers (GP5, SERPINA5, ECM1, IGHG1, and THBS1) which retained most of the diagnostic power of the overall dataset, achieving an AUC of 0.91. Taken together, this study provides a proteomic signature complementary to PSA for the diagnosis of patients with localised prostate cancer, with the further potential for assessing risk of future development of prostate cancer. Data are available via ProteomeXchange with identi- fier PXD025484.