ZNF265 is a newly identified arginine/serine-rich (SR) protein and has two transcript isoforms (ZNF265-1 and ZNF265-2) that autoregulate between each other. Previous studies have shown that ZNF265 regulates the Tra2β isoform splicing. Here, we demonstrate that two ZNF-265 transcript isoforms are expressed in various mouse tissues and that ZNF265-1 is a major isoform. The ZNF265-1 protein level in the cerebral cortex is significantly lower in relative to other tissues. The recombinant proteins of both isoforms are nuclear, in consistent with its functions as pre-mRNA splicing regulators. Splicing analysis with GluR-B and SMN2 minigenes demonstrates that ZNF265-1 inhibits the Flop exon and exon 7 usages in the splicing of two minigenes, respectively. The regulation of GluR-B and SMN2 pre-mRNA splicing by ZNF265 implies this newly identified SR protein may play important roles in maintaining normal neuronal function and SMA pathogenesis.