Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder characterized by an accumulation of glycosaminoglycans (GAGs), including heparan sulfate, in the body. Major manifestations involve the central nerve system (CNS), skeletal deformation, and visceral manifestations. About 30% of MPS II is linked with an attenuated type of disease subtype with visceral involvement. In contrast, 70% of MPS II is associated with a severe type of disease subtype with CNS manifestations that are caused by the human iduronate-2-sulfatase (IDS)-Pro86Leu (P86L) mutation, a common missense mutation in MPS II. In this study, we reported a novelIds-P88L MPS II mouse model, an analogous mutation to humanIDS-P86L. In this mouse model, a significant impairment of IDS enzyme activity in the blood with a short lifespan was observed. Consistently, the IDS enzyme activity of the body, as assessed in the liver, kidney, spleen, lung, and heart, was significantly impaired. Conversely, the level of GAG was elevated in the body. A putative biomarker with unestablished nature termed UA-HNAc(1S) (late retention time), one of two UA-HNAc(1S) species with late retention time on reversed-phase separation,is a recently reported MPS II-specific biomarker derived from heparan sulfate with uncharacterized mechanism. Thus, we asked whether this biomarker might be elevated in our mouse model. We found a significant accumulation of this biomarker in the liver, suggesting that hepatic formation could be predominant. Finally, to examine whether gene therapy could enhance IDS enzyme activity in this model, the efficacy of the nuclease-mediated genome correction system was tested. We found a marginal elevation of IDS enzyme activity in the treated group, raising the possibility that the effect of gene correction could be assessed in this mouse model. In conclusion, we established a novelIds-P88L MPS II mouse model that consistently recapitulates the previously reported phenotype in several mouse models.