We propose a panchromatic (Pan) and multispectral (MS) image fusion method in order to synthesize an MS image with enhanced spatial resolution and preserved spectral information of the original MS image. The proposed method is based on the spatial frequency and the à trous wavelet transform (SFATWT). The à trous wavelet transform (ATWT) is used to decompose Pan and MS images into low and high frequencies. The spatial frequency is exploited in the image fusion rules to improve the details or the high-frequency information which will be injected into the MS image. The ATWT reconstruction makes it possible to produce MS image with high spatial resolution. To validate the proposed method, two image sets are used. The first one is acquired by the SPOT (Satellite Pour l’Observation de la Terre) satellite with a resolution ratio of 2. The second one is the Algerian satellite AlSat 2A images with a resolution ratio of 4. The fused results are evaluated by means of qualitative and quantitative comparisons. The assessment of fused products has shown that the proposed method is promising.