To efficiently protect the ownership of multimedia data with watermarking technology, a novel image watermarking algorithm based on discrete wavelet transform (DWT) and memetic algorithm (MA) is proposed in this paper. The watermark is embedded to subband coefficients of subimage which is extracted from the original image with DWT, and watermark extraction is efficiently performed via MA. Experimental results show that the proposed watermarking algorithm results in almost invisible difference between the watermarked image and the original image, and is robust to common image processing operations and JPEG lossy compression.