This book constitutes the thoroughly refereed papers of the Second International Conference on Applied Informatics, ICAI 2019, held in Madrid, Spain, in November 2019. The 37 full papers and one short paper were carefully reviewed and selected from 98 submissions. The papers are organized in topical sections on bioinformatics; data analysis; decision systems; health care information systems; IT Architectures; learning management systems; robotic autonomy; security services; socio-technical systems; software design engineering.