The androgen receptor (AR) is a ligand-activated transcription factor which controls growth and survival of prostate cancer cells. In the present study, we investigated the regulation of AR activity by the receptor interacting protein RIP140. We first showed that RIP140 could be co-immunoprecipitated with the receptor when co-expressed in 293T cells. This interaction appeared physiologically relevant since ChIP assays revealed that under R1881 treatment, RIP140 could be recruited to the PSA encoding gene in LNCaP cells. In vitro GST pull-down assays evidenced that the carboxy-terminal domain of AR could interact with different regions of RIP140. By means of fluorescent proteins we demonstrated that ligand-activated AR was not only able to translocate to the nucleus but also to relocate RIP140 from very structured nuclear foci to a diffuse pattern. Overexpression of RIP140 strongly repressed AR-dependent transactivation by preferentially targeting the ligand binding domain-dependent activity. Moreover, disruption of RIP140 expression induced AR overactivation thus revealing RIP140 as a strong AR repressor. We analyzed its mechanism of transrepression and first demonstrated that different regions of RIP140 could mediate AR-dependent repression. We then showed that the carboxy-terminal end of RIP140 could reverse transcriptional intermediary factor TIF2-dependent overactivation of AR. The use of mutants of RIP140 allowed us to suggest that CtBP played no role in RIP140-dependent inhibition of AR activity whereas HDACs partly regulated that transrepression. Finally, we provided evidence for a stimulation of RIP140 mRNA expression in LNCaP cells under androgen treatment, further emphasizing the role of RIP140 in androgen signaling.