The effect of the pre-selection of particle size range on the treatment of locally-sourced bentonite clay from logomani, North-Eastern Nigeria using aqueous acid and alkali solution has been studied. Characterization of the clay adsorbents was done via Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction analyses (XRD). The acid and alkali modified clay adsorbents were applied in the removal of methylene blue from aqueous media. The highest adsorbed amount (51.196mg/g) which represents 91.421% for the HCl-treated clay was obtained with the clay particle size range of < 63μm treated with 0.5M HCl. While on the other hand, the lowest adsorbed amount of 24.726mg/g which represents 44.154% for the HCl-treated clay was obtained with the clay particle size range of 106-125μm treated with 2.5M HCl. A similar trend was also observed for the H2SO4-treated clay in which case the highest value of Qt (42.636mg/g)which represents 76.137% was obtained with particle size range of < 63μm treated with 0.5M H2SO4 and the lowest value of Qt (24.632mg/g) which represents 43.986% with particle size range of 106-125μm treated with 2.5M H2SO4. Generally, the values for amount adsorbed Qt, obtained for the clays treated with alkali solutions were higher. The optimum adsorptive capacity for the alkali-treated clay was 52.190mg/g, which represents 93.196%. This was obtained with the clay treated with 0.5M NaOH and the lowest, 43.713mg/g, which represents 78.059% which was obtained with the particle size range of 106-125μm. In general, the values for amount adsorbed Qt, obtained for the clay samples for which particle size was pre-selected prior to treatment were greater than the values for the unselected clay.