The prostate cancer (PCa) risk-associated SNP rs11672691 is positively associated with aggressive disease at diagnosis. We showed that rs11672691 maps to the promoter of a short isoform of long noncoding RNA PCAT19 (PCAT19-short), which is in the third intron of the long isoform (PCAT19-long). The risk variant is associated with decreased and increased levels of PCAT19-short and PCAT19-long, respectively. Mechanistically, the risk SNP region is bifunctional with both promoter and enhancer activity. The risk variants of rs11672691 and its LD SNP rs887391 decrease binding of transcription factors NKX3.1 and YY1 to the promoter of PCAT19-short, resulting in weaker promoter but stronger enhancer activity that subsequently activates PCAT19-long. PCAT19-long interacts with HNRNPAB to activate a subset of cell-cycle genes associated with PCa progression, thereby promoting PCa tumor growth and metastasis. Taken together, these findings reveal a risk SNP-mediated promoter-enhancer switching mechanism underlying both initiation and progression of aggressive PCa. Display omitted •rs11672691 risk region is bifunctional with both promoter and enhancer activity•This SNP modulates the bifunctionality and reciprocal expression of PCAT19 isoforms•PCAT19-long interacts with HNRNPAB to activate a subset of cell-cycle genes•PCAT19-long regulates cell proliferation, tumor growth, and metastasis Transcription factor binding site remodeling by a risk allele for aggressive prostate cancer results in conversion of a promoter to an enhancer with downstream consequences on long noncoding RNA isoform expression and oncogenesis.