SummaryMany metazoan genes express alternative long 3′ UTR isoforms in the nervous system, but their functions remain largely unclear. In Drosophila melanogaster, the Dscam1 gene generates short and long (Dscam1-L) 3′ UTR isoforms due to alternative polyadenylation (APA). Here, we found that the RNA-binding protein Embryonic Lethal Abnormal Visual System (Elav) impacts Dscam1 biogenesis at two levels, including regulation of long 3′ UTR biogenesis and skipping of an upstream exon (exon 19). MinION long-read sequencing confirmed the connectivity of this alternative splicing event to the long 3′ UTR. Knockdown or CRISPR deletion of Dscam1-L impaired axon growth in Drosophila. The Dscam1 long 3′ UTR was found to be required for correct Elav-mediated skipping of exon 19. Elav thus co-regulates APA and alternative splicing to generate specific Dscam1 transcripts that are essential for neural development. This coupling of APA to alternative splicing might represent a new class of regulated RNA processing. Graphical AbstractHighlightsElav regulates Dscam1 long 3′ UTR (Dscam1-L) biogenesisLong-read sequencing reveals connectivity of long 3′ UTR to skipping of upstream exon 19Loss of Dscam1-L impairs axon outgrowthDscam1 long 3′ UTR is required for correct splicing of exon 19