High resolution multi-spectral (HRMS) images are essential for most of the practical remote sensing applications. Pansharpening is an effective mechanism to produce HRMS image by integrating the signiﬁcant structural details of panchromatic (PAN) image and rich spectral features of multi-spectral (MS) images. The traditional pansharpening methods incur disadvantages like spectral distortion, spatial artifacts and lack of details preservation in the fused image. The pansharpening approach proposed in this paper is based on integrating wavelet decomposition and convolutional sparse representation (CSR). The wavelet decomposition is performed on PAN and MS images to obtain low-frequency and high-frequency bands. The low-frequency bands are fused by exploring the CSR based activity level measurement while the high-frequency bands are fused based on the constituent wavelet energy. Finally, the HRMS image is restored by implementing the inverse transform on fused bands. The fusion rules are constructed, thus to transfer the crucial details from source images to the fused image effectively. The proposed method produces HRMS images with rational spatial and spectral qualities at relatively less computational effort compared with most of the traditional sparse representation methods. The visual outcomes and quantitative measures approve the eminence of the proposed fusion framework.