Updated publication reference for PubMed record(s): 33976187. Androgen signaling through the androgen receptor (AR) regulates multiple pathways in both normal and prostate cancer cells. Androgen regulates diverse aspects of the AR life cycle, including its post-translational modification, but understanding how specific modifications influence AR activity has been mostly elusive. Here, we show that androgen regulates AR through a pathway mediated by the mono-ADP ribosyltransferase, Parp7. We show that Parp7 ADP-ribosylates AR on multiple cysteines, and that a subset of these sites mediates agonist-specific recruitment of the E3 ligase Dtx3L/Parp9. Tandem macrodomains in Parp9 selectively recognize ADP ribosylated AR, and Dtx3L/Parp9 affects expression of a subset of AR-regulated genes. Parp7, ADP-ribosylation of AR, and AR-Dtx3L/Parp9 complex assembly are inhibited by 60 Olaparib, a compound used clinically to inhibit poly-ADP-ribosyltransferases Parp1/2. Our study reveals the components of a new androgen signaling axis that uses a writer and reader of ADP-ribosylation to modulate AR activity.