In this paper, we introduce a new robust image watermarking technique based on the Discrete Wavelet Transform (DWT). The proposed method extends the concept of image denoising to watermarking. A spatially adaptive wavelet thresholding method is used to select the coefficients to be water-marked. A multi-bit watermark is embedded into the discrete wavelet coefficients of the host image. A semi-blind water-mark extraction algorithm is presented and the threshold for a given probability of false alarm is derived. The simulation results show that the proposed method outperforms a well-known DWT based watermarking method under most attacks including JPEG compression.