A modified code division multiple-access (MCDMA) technique is constructed by the spread-spectrum technique and a mix coder, and then it is used to configure a multiple-watermarking scheme for still images. Another type of multiple-watermarking scheme, non-code-division multiple-access watermarking (NCMW), is used to demonstrate that the MCDMA scheme is superior. In the embedding process, three watermark bits are modulated to the five-bit MCDMA code. Then the 15 MCDMA bits are concealed in the coefficients of a group that consists of four DCT blocks. Empirical results show that our proposed scheme can sustain attacks like JPEG lossy compression, rotation, resizing, cropping, painting, noising, and blurring. Compared with other multiple-watermarking schemes, our proposed method has two advantages: (1) The secret image has very high security owing to the use of MCDMA for digital communication. (2) The extracted watermarks have the same quality under all kinds of attacks, whereas other schemes yield different extracted-watermark quality.