AATF is a predominantly nuclear protein that has been shown to be an apoptosis-inhibiting factor essential for both embryonic development and tumor growth. Several studies have shown a role of AATF in the modulation of pivotal cellular signal transduction pathways such as p53-, mTOR- and HIF-signaling. However, the exact molecular functions underlying its essential nature to cell proliferation and survival have remained elusive. Interestingly, several lines of evidence point towards a pivotal role of this protein in ribosome biogenesis and the maturation of ribosomal RNA. The function of AATF in this process is not clear, especially since the identity of the RNA-binding protein that links the AATF-containing protein complex (ANN) to rRNA precursors is unknown. In this study, we identify AATF in a screen for RNA-binding proteins. Importantly, AATF does not only bind to polyA-tailed RNA but CLIP-experiments reveal its association with ribosomal RNA. The RNA-binding domain of AATF is essential to maintain its positive effect on cellular rRNA levels. Furthermore, AATF binds to both mRNAs encoding for ribosome biogenesis factors as well as proteins involved with this process indicating AATF to be a central hub for the coordination of ribosome maturation. Consequently, our data for the first time identify the molecular basis to the role of AATF in ribosome biosynthesis and corroborate the link between tumorigenesis and ribosome biology.