Acid- and alkali-modified tapioca starches (ACMSs and ALMSs) were prepared without neutralization reactions, using the tray-drying method. Physicochemical properties and tablet evaluations of ACMSs and ALMSs were investigated, which the modified starches in the particles size range of 75–150 μm were used. Both types of modified starches possessed higher temperature and enthalpy of gelatinization and greater % relative crystallinity than the native starches. Changes in thermal behaviors at high temperatures of ACMSs and ALMSs in the solid state were revealed by DSC. The ACMS and ALMS dispersions presented lower thixotropic properties and viscosity than the native starch dispersions. However, the ALMS dispersion showed higher thixotropy and viscosity than the ACMS dispersions. ALMSs gave higher bulkiness than ACMSs, leading to lower flowability and compressibility. The hardness of the ACMS tablets was higher than that of the ALMS tablets because the rougher surface of ACMS granules could promote cold welding of the interparticulate contact area. However, the disintegration time and drug dissolution rate in both acidic and neutral media for the ACMS tablets were similar to those of the ALMS tablets. These findings indicated that ACMSs display better powder characteristics than ALMSs for use as tablet diluents.