In the today’s world of rapidly growing internet services (Commercial and educational), security always comes in picture even at low level. Same way in the field of Information Technology and Computer Science and Engineering, security is always the first requirement. If we take an example of audio, video, images in which sometimes it is required to prove our ownership, to secure our data or information some means of security is always required. So, this paper illustrates ideas for making our own images to be secured from unauthorized persons, which can also be applied to videos and audios in terms. The process of making changes into images to secure it is called “IMAGE WATERMARKING”. There are various ways to watermark images. The concept, considered in this paper is to hide image (watermark) behind cover image (which needs to be owned) and this concept is explained using DCT [Discrete Cosine Transform].In which both, cover image and watermark image, are converted in DCT forms. Then watermark image is embedded into cover image. Finally, IDCT [Inverse Discrete Cosine Transform] is applied on DCT formed watermarked cover image to get watermarked image in which watermark is invisible. To check the effect we can try to extract watermark from watermarked image and we can notice similarities between original watermark and extracted one. Then to check robustness of this watermarking technique we can apply some attacks on watermarked image and then we can extract watermark from it to check similarities between original watermark and extracted one using PSNR[Pick Signal to Noise Ratio]values.