This paper deals with the hygrothermal stress induced in a polymeric thin film deposited on Si wafer subjected to the combined influence of temperature change and moisture absorption. The laser scanning method and the boundary element method (BEM) are employed to investigate the residual stresses. The film/wafer system is assumed to be linearly elastic. The film/substrate system is assumed to be stress-free at a temperature of C o 300 and is cooled from a cure temperature down to room temperature. Then the moisture concentration in the film is increased to the saturation level. The normal stress across thickness of the thin film is estimated from wafer curvature measurements. The boundary element method is employed to investigate the whole stresses in the film. The numerical results for the normal stress across thickness of the film show good agreement with experimental results obtained by using the laser scanning method. The singular stress is observed near the interface corner. Such residual stresses are large enough to initiate interface delamination to relieve the residual stresses.