Inflammatory bowel disease (IBD) is characterized by an inappropriate and persistent inflammatory immune response and is often accompanied by excessive reactive oxygen species (ROS) production. For effective IBD treatment, there is a high demand for safe and targeted therapy that can be orally administered. In this study, we aimed to propose the use of inflamed colon-targeted antioxidant nanotherapeutics (ICANs) for in situ oxidative stress level modulation in colitis. ICANs consist of mesoporous silica nanoparticles (MSNs) with surface-attached ROS-scavenging ceria nanoparticles (CeNPs), which are further coated with poly(acrylic acid) (PAA) to facilitate preferential adherence to inflamed colon tissues through electrostatic interaction. We achieved a high ROS-scavenging property that remained effective even after artificial gastrointestinal fluid incubation by optimization of the molecular weight and PAA-coating pH. The orally administered ICANs demonstrated enhanced adherence to inflamed colon tissues in an acute inflammation mouse model of IBD induced by dextran sulfate sodium. This targeted delivery resulted in gut microenvironment modulation by regulating redox balance and reducing inflammatory cell infiltration, thereby suppressing the colitis-associated immune response. These findings highlight the potential of noninvasive ICANs as a promising candidate for treating inflammatory intestinal diseases by oxidative stress level modulation in colitis.