In this paper, we have developed a robust object-based watermarking algorithm using the scale-invariant feature transform (SIFT) features in conjunction with a new data embedding method based on discrete cosine transform (DCT). The message is embedded in DCT spaces of randomly generated blocks in the selected object region. To recognize the object region after being distorted, its SIFT features are registered in advance. In the detection scheme, we firstly detect the object region by using feature matching. The transformation parameters are then calculated, and the message can be detected. Experimental results demonstrated that our proposed algorithm is very robust to geometrical distortions such as JPEG compression, scaling, rotation, shearing, aspect ratio change, image filtering, and so on.