1/f noise and nonlinear effects in Cadmium Oxide thin films for different current densities on varying the thickness of the films, at room temperature are studied. The specific dependence of 1/f noise on the thickness of the film, the effect of current densities on 1/f noise for the films of various thicknesses (300 Å to 750 Å) has been investigated. It is noticed that, for a constant current, the thickness of the film leads to an increase of 1/f noise. 1/f noise plays an important role in choosing frequency band in which a device can be effectively used. Cadmium oxide thin films are regarded as a material with many attracting properties such as large energy band gap, good conduction, high transmission coefficient etc. It is specially used in optoelectronic devices.