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Transcripts derived from centromere repeats play a critical role in the localization and activity of kinetochore components during mitosis such that disruption of RNA polymerase II-dependent transcription compromises the fidelity of chromosome segregation. Here, we show that the retinoblastoma tumor suppressor protein (RB), a critical regulator of the G1/S cell cycle transition, additionally plays an important role in the regulation of centromere transcription during mitosis. We find that cells lacking RB experience increased RNA Polymerase II activity at mitotic centromeres and a corresponding increase in nascent RNA transcripts derived from centromere sequences. Together with high levels of centromere transcription and corresponding R-loop formation, RB-deficient cells exhibit centromere DNA breaks and local activation of ATR that correspond with increased centromere localization of Aurora B, destabilization of kinetochore-microtubule attachments, and an increase in anaphase defects. Importantly, reduction of DNA damage, ATR activity, and mitotic defects following inhibition of RNA Pol II, or targeted repression of centromere transcription through centromere tethering of Suv420h2, support that mitotic defects in RB-deficient cells are linked to centromere transcription.