The present study involves the photocatalytic degradation of dyes [Rhodamine B and methylene blue], employing heterogeneous catalysis. The photocatalytic activity of copper oxide (CuO) has been investigated. An attempt has been made to study the effect of different parameters such as amount of catalyst, concentration of dye, pH and intensity of light. The rate of decolourization was estimated from residual concentration spectrophometrically. The experimental results indicated that the maximum decolourization (near about 80%) of dyes occurred at basic pH, (10.0 and 8.5). It was observed that photocatalytic degradation of dyes follows pseudo first order kinetics. A tentative mechanism has also been proposed for the photocatalytic degradation of dyes in presence of copper oxide semiconductor.