In the present work, polyelectrolyte multilayer thin films of nanometre precision was fabricated by layer-by-layer (L-b-L) assembly of oppositely charged chitosan and dextran sulphate on silicon wafer. The effect of pH, polymer concentration, ionic strength and the number of layers during assembly on film thickness and surface roughness was studied. The thickness of the film was measured using Ellipsometry and the surface roughness by Atomic Force Microscopy (AFM). For a given number of layers and ionic strength, the thickness of the multilayer film gradually increased, whereas the roughness increased with increase in ionic strength, but it decreased with increase in number of layers. The thickness increased with increase in pH up to 6 and above which there was a decreasing trend. The maximum roughness was observed at pH 5, above which it decreased again. For an increase in polymer concentration, the thickness increased and roughness showed decreasing trend. Morphology and surface roughness studies using AFM revealed clear loops and porous structure at the surface of chitosan-dextran sulphate multilayer thin films. The fabricated multilayers are subjected to post treatment with both salt and water.