Mucopolysaccharidosis type II (MPS II, OMIM 309900) is an X-linked recessive lysosomal storage disorder caused by the accumulation of heparan sulfate and dermatan sulfate due to iduronate-2-sulfatase (IDS) enzyme deficiency. To detect IDS gene mutation, DNA samples are obtained from 10 MPS II patients and 50 normal individuals, then the exon 1 of IDS gene was analyzed with Sanger sequencing. Two novel mutations are found from one male patient at the site of c.22C>A (p.Arg8=) and c.54C>A (p.Ser18Arg). Both mutations are not located in the bases which are responsible as the signal peptide cleavage site. Amino acid substitution c.54C>A (p.Ser18Arg) does not change the hydrophobic characteristic as both amino acids are hydrophobic. Therefore, those mutations do not change IDS enzyme structure nor alter the signaling pathway of IDS mRNA-ribosome complex to the endoplasmic reticulum. This study of exon 1 is the first to be performed in Indonesia. The novel mutations found in this study can contribute to a single nucleotide polymorphism (SNP) database of MPS II patients from all over the world, thus it leads to a deeper understanding of this rare disease at the molecular level. Therefore, a genotype study is needed to get a full profile of MPS II patients in Indonesia.