The carbonaceous adsorbents with controllable pore sizes were prepared from carbonized fir wood (i.e., char) by KOH and steam activation. Pore properties of the carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were characterized from N2 isotherms. Through varying KOH/char ratio from 0.5 to 6, the KOH-activated carbons exhibited the surface area ranging from 891 to 2794 m2 g−1 with a fraction of micropore volume of 0.76–0.82. On the other hand, carbons activated by steam at 900 °C for 5 and 7 h had a surface area of 1016 and 1131 m2 g−1 with a fraction of micropore volume of 0.51 and 0.48, respectively. The kinetics of adsorption of methylene blue, basic brown 1, acid blue 74, 2,4-dichlorophenol, 4-chlorophenol, p-cresol, and phenol from water on all the carbons studied were examined to check their chemical characteristics. The effective particle diffusivities within carbon particles were also evaluated.