Several lines of evidence point to a role for noncoding RNA in transcriptional repression by Polycomb group (PcG) proteins, but the precise mechanism remains unclear. Here we show that human MOV10, a putative RNA helicase previously implicated in post-transcriptional gene silencing, co-purifies and interacts with components of Polycomb-repressive complex 1 (PRC1) from human cells. Endogenous human MOV10 is mostly nuclear, and a proportion associates with chromatin in an RNA-dependent manner. Small hairpin RNA (shRNA)-mediated knockdown of MOV10 in human fibroblasts leads to the upregulation of the INK4a tumor suppressor, a known target of PcG-mediated repression, accompanied by the dissociation of PRC1 proteins from the locus and a reduction in trimethylation of histone H3 on Lys27 (H3K27me3). As well as prompting reassessment of MOV10's role in other settings, our findings suggest that it is directly involved in transcriptional silencing by PcG complexes.