The nucleoside diphosphate-linked moiety X-type motif 15 genes were high frequency of NUDT15 variants in Asian and affected the metabolism of 6-mercaptopurine, a prolonged backbone of acute lymphoblastic leukemia treatment (ALL). The patients with NUDT15 variants failured in 6-MP metabolism, leading to increased mortality risk. Aims: This study reports the frequency of NUDT15 variants in children with ALL at Children’s Hospital 2. Methods: A total of 220 patients with ALL were identified NUDT15 variants on exon 1 and exon 3 in chromosome 13 by Sanger sequencing. Results: We identified five variants of NUDT15, including *1, *2, *3, *5, *6 (87%; 2,7%; 6,9%; 0,9% và 2,5%; respectively). We didn’t identify *4 in our study. The NUDT15 genotyping showed 25% of patients with NUDT15 variants: heterozygous (24.1%) and homozygous/compound heterozygous (0.9%). Conclusion: NUDT15 variants were presented in one-fourth of the participants. To the personalized medicine of 6-MP, testing for NUDT15 polymorphisms prior to therapy is warranted.