This paper investigates the feasibility of watermark embedding in the discrete cosine transform (DCT) domain for binary images. Watermark embedding is known to be difficult for binary images due to their binary nature. For frequency domain approach to binary image watermarking, a post-embedding binarization is a necessary step to ensure that the watermarked image is still a binary image. This step disturbs the watermark embedded and is likely to remove the watermark. We have succeeded in combating this interference by embedding watermarks in the DC components of DCT and employing a biased binarization threshold. This algorithm can be applied to binary images in general and experiments show that the embedding algorithm proposed can not only survive binarization, but also provide some degree of robustness against common image processing.