We propose a novel watermarking scheme for images which optimizes the watermarking strength using Harmony Search Algorithm (HSA). The optimized watermarking scheme is based on the discrete wavelet transform (DWT) and singular value decomposition (SVD). The amount of modification made in the coefficients of the LL3 sub band of the host image depends on the values obtained by the Harmony Search algorithm. For optimization of scaling factors, HSA uses an objective function which is a linear combination of imperceptibility and robustness. The PSNR and SSIM values show that the visual quality of the signed and attacked images is good. The proposed scheme is robust against common image processing operations. It is concluded that the embedding and extraction of the proposed algorithm is well optimized, robust and show an improvement over other similar reported methods.