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.