Updated project metadata. During microRNA-biogenesis, stem-loop structured precursors are processed in two endonucleolytic steps, giving rise to mature microRNAs (miRNAs). This process is not only regulated at the level of transcription but also posttranscriptionally by RNA-binding proteins (RBPs). Here we have used a proteomics-based pull-down approach to map and characterize the interactome of 72 pre-miRNAs in eleven cell lines. We identify over 150 RBPs that interact specifically with distinct pre-miRNAs. To demonstrate their functional relevance, we used RNAi knockdown and CRISPR/Cas-mediated knockout experiments and analyzed changes in miRNA levels. Indeed, a large number of the investigated candidates have effects on miRNA-processing under our experimental conditions, including several C3H-zinc-finger proteins. Ultimately, we show that TRIM71/Lin41 is a potent regulator of miR-29a processing and its inactivation directly affects miR-29a targets. In summary, we provide an extended database of RBPs that interact with pre-miRNAs in different cell types helping to elucidate posttranscriptional regulation of miRNA biogenesis on a global scale.