The smart healthcare system is one of the Internet of Things‐based applications that are increasingly used nowadays. One of the requirements of this system is privacy‐preserving, which should protect the disclosure of the patient record contents. In the present paper, a combination of chaotic functions and a new DNA‐based steganography method, and image blocking are suggested to protect patients' privacy‐preserving. First, the image is blocked, and the initial key for the chaotic function will be gained by using the centers of the blocks. Then the data and image are transformed into DNA sequences. Finally, one of the randomly chosen DNA strands of data is XOR with the center of one randomly selected block and will be placed in one of the block pixels. The failure to send the initial key separately to generate random numbers, as well as the random selection of secret data bits and image pixels for steganography has increased the security of the proposed method. The simulation results not only indicate the quality of the stego‐image but also show better performance of the proposed method than the existing methods.