By a combination of small angle neutron scattering (SANS) and theological measurements, characterization of colloidal silica suspensions in aqueous (hydroxypropyl)methylcellulose (HPMC) solutions and their shear viscosities and dynamic moduli measurements were performed as functions of concentrations of silica and HPMC and temperature. From the SANS measurements, adsorption of HPMC induced no changes in particle packing in the silica suspensions, indicating no formation of aggregates. The amounts of HPMC adsorbed on the silica surfaces decreased with an increase in the silica content, due to the ordered structure within the silica suspensions. The shear viscosity increased with an increase in adsorption time as well as silica concentration due to an increase in the adsorbed amount, and it showed shear thinning. When the temperature was lowered, the shear viscosity increased and viscoelastic responses were enhanced because of an increase in the effective hydrodynamic layer thickness and a higher probability of occurring in the chain entanglements and polymer bridging under better solvent conditions.