Arginine methylation is a common post-translational modification (PTM) that regulates numerous biological processes, including transcription, splicing, and signal transduction. This modification is catalyzed by nine protein arginine methyltransferases (PRMTs), which transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the guanidino group of arginine residues in substrate proteins. PRMTs are classified into three types: type I (PRMT1, 2, 3, 4, 6, and 8) enzymes generating ω-N^G-monomethyl arginine (MMA) and ω-N^G,N^G-asymmetric dimethylarginine (ADMA), type II (PRMT5 and 9) enzymes generating MMA and ω-N^G,N’^G-symmetric dimethylarginine, and type III (PRMT7) enzyme producing only MMA. PRMT4, also known as coactivator-associated arginine methyltransferase 1 (CARM1), is overexpressed in several cancer and exhibits both oncogenic and tumor suppressive functions, so its exact role in tumorigenesis still remains controversial. To gain a clearer understanding of the biological function of CARM1, it is crucial to identify its novel substrates and elucidate their roles in biological systems. In this study, we identified PI3KC2α as a novel CARM1 substrate, which regulates microtubule dynamics. CARM1 methylates PI3KC2α, which increases its protein stability. In addition, our data show that CARM1-PI3KC2α axis contributes to microtubule formation and stabilization. Taken together, our findings suggest that arginine methylation by CARM1 finely tunes the function of PI3KC2α in microtubule dynamics.