Post-translational modifications of proteins play a critical role in the DNA damage response and in the maintenance of genome stability. However, the role of arginine methylation in these processes is poorly understood. Here, it is revealed that the arginine methyltransferase PRMT5 is a key regulator of DNA double strand break (DSB) repair through targeting RUVBL1, a critical cofactor of the Tip60 complex, for methylation at R205. RUVBL1-R205 methylation is required for Tip60-mediated H4K16 acetylation and the mobilisation of 53BP1 from DNA breaks ends, enabling DNA resection and homologous recombination repair of DSBs. Interestingly, RUVBL1 methylation is not required for Tip60-mediated ATM activation, demonstrating that PRMT5-mediated methylation of RUVBL1 is able to regulate specific activities of the Tip60 complex in response to DSBs.