A range of chitosan stabilized copper (chi-Cu) nanoparticles have been prepared and characterized using UV-Vis, TEM and FTIR. The chi:Cu ratios affect the morphologies and sizes of the outcome Cu particles. The rate constant (k) of the catalytic reduction of p-nitrophenol follows the decreasing trend of the chi:Cu ratio viz. 2:1 > 4:1 > 6:1 > 1:5. These trends are believed to be closely related to the size and accessibility to the Cu particles in the colloids.