Background: Mechanistic hypotheses suggest that vitamin D may be involved in prostate carcinogenesis through various effects on differentiation, apoptosis, and cell proliferation. Plasma parathyroid hormone (PTH) concentration, closely related to vitamin D metabolism may also play a role in prostate carcinogenesis. However, epidemiological evidence regarding the relationship between vitamin D status and prostate cancer risk is inconsistent and only one prospective study has investigated the association between PTH concentration and prostate cancer risk. Our objectives were thus to prospectively investigate the associations between vitamin D status, selected polymorphisms of vitamin D-related genes, plasma PTH concentration and prostate cancer risk. Methods: 184 cases diagnosed within the SU.VI.MAX cohort were included in a nested case–control study and matched to 368 controls (13 years of follow-up). Baseline total plasma 25-hydroxyvitamin D (25OHD) concentration was assessed with Roche Cobas electrochemoluminescent assay and plasma PTH was measured through Roche Cobas electrochemoluminescent immunometric assay. Single nucleotide polymorphisms were determined with TaqMan assay (VDR BsmI, FokI and Cdx2, CYP24A1 rs4809958, GC rs4588 and rs7041, RXR rs7861779 and rs12004589, CaSR rs1801725 and rs4678174). Multivariate conditional logistic regression models were computed. Results: Higher 25OHD concentration was inversely associated with the risk of prostate cancer in normal-weight men (OR per 1 ng/ml increment = 0.91 (0.84, 0.98), P trend = 0.02), but not in overweight men (P = 0.1). Higher PTH concentration was inversely associated with prostate cancer risk (OR per 1 ng/L = 0.96 (0.94, 0.99), P trend = 0.006: OR:Q4 vs Q1 = 0.44 (0.24, 0.79), P trend = 0.01). The studied SNPs were not associated with prostate cancer risk. Conclusions: Our results suggest that vitamin D may be beneficial against prostate cancer in normal-weight men and that higher plasma PTH concentration may be associated with a decreased risk of prostate cancer, independently from 25OHD concentration. These associations, supported by biological plausibility, provide interesting insights into the understanding of the role of vitamin D and PTH in the etiology of prostate carcinogenesis and deserve further exploration.