This book constitutes the refereed proceedings of the 12th International Conference on the Quality of Information and Communications Technology, QUATIC 2019, held in Ciudad Real, Spain, in September 2019. The 19 full papers and 6 short papers were carefully reviewed and selected from 66 submissions. The papers are organized in topical sections: security & privacy, requirements engineering, business processes, evidence-based software engineering, process improvement and assessment, model-driven engineering & software maintenance, data science & services, and verification and validation.