The CCIS book constitutes selected papers of the 12th International Conference on Computational Science and Computational Intelligence, CSCI 2025, which took place in Las Vegas, NV, USA, during December 3–5, 2025.The 30 papers and 2 poster papers included in this book were carefully reviewed and selected from the following tracks: 24 papers have been selected from 169 submissions to the Research Track on Signal & Image Processing, Computer Vision & Pattern Recognition, CSCI-RTPC; 4 papers stems from 70 submissions to the Research Track on Cloud Computing and Data Centers, CSCI-RTCC; and 4 papers out of 52 submissions have been selected from the Research Track on Mobile Computing, Wireless Networks, & Security, CSCI-RTMC.The papers have been organized in topical sections as follows: Imaging Science and Application- Detection Methods; Signal & Image Processing, Computer Vision, Pattern Recognition, and Applications; Cloud Computing, Data Centers, and Related Issues; Mobile Computing, Wireless Networks, Security, and Applications; and Poster Papers.